INST 240 (Pressure and Level Measurement), section 1

Lab

Pressure measurement loop: Questions 91 and 92, completed objectives due by the end of day 4,section 2Bulleted questions following lab objectives to be reviewed orally during lab time on day 4, section 2

Feedback questions

Questions 81 through 90, due at the end of day 4

Exam

Day 5 of next section – only a simple calculator may be used!Question 93 previews the mastery exam circuit-building activity

Recommended daily schedule

Day 1

Theory session topic: Concepts of pressure and pressure unit conversions

Questions 1 through 20; answer questions 1-10 in preparation for discussion (remainder for practice)

Day 2

Theory session topic: Pressure measurement technologies

Questions 21 through 40; answer questions 21-28 in preparation for discussion (remainder for practice)

Day 3

Theory session topic: Instrument calibration

Questions 41 through 60; answer questions 41-50 in preparation for discussion (remainder for practice)

Day 4

Theory session topic: Electronic pressure measurement

Questions 61 through 80; answer questions 61-70 in preparation for discussion (remainder for practice)

Feedback questions (81 through 90) due at the end of the day

1

INST 240 (Pressure and Level Measurement)

Credits/hours: 6 credits = 108 clock hours

Prerequisite or corequisite: INST 200 (Introduction to Instrumentation)

Course description: In this course you will learn how to precisely measure both fluid pressure andfluid/solids level in a variety of applications, as well as accurately calibrate and efficiently troubleshootpressure and level measurement systems.

Program outcomes addressed:

(1) Communication; Communicates and expresses thoughts across a variety of mediums (verbal, written,visually) to effectively persuade, inform, and clarify ideas with colleagues.

(2) Time management; Arrives on time and prepared to work; budgets time and meets deadlines whenperforming technical tasks and projects.

(3) Safety; Complies with national, state, and local safety regulations when repairing, calibrating, andinstalling instruments.

(4) Diagnose and repair existing instruments; Assesses, diagnoses, and repairs faulty instruments inmeasurement and control systems using logical procedures and appropriate test equipment.

(5) Install and configure new instruments; Builds, configures and installs new instrument systemsaccording to plans, applying industry construction standards, and ensuring correct system operationwhen complete.

(7) Calibrate instruments; Assesses instrument accuracy and corrects inaccuracies using appropriatecalibration procedures and test equipment.

(8) Document instrument systems; Interprets and creates technical documents (electronic schematics,loop diagrams, and P&IDs) according to industry (EIA, ISA) standards.

(9) Self-directed learning; Selects and researches relevant information sources to learn newinstrumentation principles, technologies, and techniques.

Instructor contact information:

Tony Kuphaldt

Desmond P. McArdle Center

Bellingham Technical College

3028 Lindbergh Avenue

Bellingham, WA 98225-1599

(360)-752-8477 [office phone]

(360)-752-7277 [fax]

tkuphald@btc.ctc.edu

Required materials:

• Socratic worksheets: INST240 sec1.pdf, INST240 sec2.pdf, INST240 sec3.pdf, INST240 sec4.pdf

→ Download at: http://openbookproject.net/books/socratic/sinst

• Lessons in Industrial Instrumentation, By Tony R. Kuphaldt. Useful for all quarters of instruction.

→ Download at: http://openbookproject.net/books/socratic/sinst/book/liii.pdf

• Spiral-bound notebook for reading annotation, homework documentation, and note-taking. A separatenotebook for each course is recommended.

• Instrumentation reference CD-ROM (free, from instructor). This disk contains many tutorials anddatasheets in PDF format to supplement your textbook(s).

• Tool kit (see detailed list)

• Simple scientific calculator (non-programmable, non-graphing, no unit conversions, no numerationsystem conversions), TI-30Xa or TI-30XIIS recommended

2

Supplemental materials: (recommended, not required)

• “BTCInstrumentation” channel on YouTube (http://www.youtube.com/BTCInstrumentation), hostsa variety of short video tutorials and demonstrations on instrumentation.

• Instrumentation, by Franklyn W. Kirk, published by American Technical Publishers. ISBN-10:0826934234 ; ISBN-13: 978-0826934239. This text is light on detail and math, but does a good jobintroducing all the major principles and technologies in simple language. Excellent photographs andillustrations, too. Useful for all three quarters of instruction.

• Instrument Engineer’s Handbook, Volume 1: Process Measurement and Analysis, edited by Bela Liptak,published by CRC Press. 4th edition ISBN-10: 0849310830 ; ISBN-13: 978-0849310836.

• Purdy’s Instrument Handbook, by Ralph Dewey. ISBN-10: 1-880215-26-8. A pocket-sized field referenceon basic measurement and control.

• Cad Standard (CadStd) or similar AutoCAD-like drafting software (useful for sketching loop andwiring diagrams). Cad Standard is a simplified clone of AutoCAD, and is freely available at:http://www.cadstd.com

• Any good introductory physics textbook (Applied Physics by Tippens, or Conceptual Physics by Hewitt)

• CRC Handbook of Chemistry and Physics

Student performance objectives:

Assessment legend: [P] = Preparation, [L] = Lab, [F] = Feedback questions, [X] = Exam

• Mastery (must eventually be demonstrated without error)

• [L] Proper use of deadweight tester as a calibration standard

• [L] Proper use of U-tube manometer as a calibration standard

• [L] Calibration of an electronic pressure transmitter to specified range and accuracy

• [L] Calibration of a pneumatic liquid level transmitter to specified range and accuracy

• [L] Create accurate as-built loop diagrams

• [L] Correctly identify common pipe and instrument tube fittings

• [L] Troubleshoot a problem within an electronic (4-20 mA loop) pressure measurement system, given aspecified time to logically identify the location and nature of the problem

• [L] Troubleshoot a problem within a pneumatic (3-15 PSI loop) level measurement system, given aspecified time to logically identify the location and nature of the problem

• [L] Work safely and constructively within a team

• [X1] Build a circuit to energize an electromechanical relay

• [X1] Convert between gauge and absolute pressure measurements

• [X1] Convert between different pressure units – only a simple calculator may be used!

• [X1] Calculate force, pressure, or area given the other two variables

• [X1] Identify proper use of ∆P instrument for pressure/vacuum measurement

• [X1] Calculate instrument calibration points given ranges

• [X1] INST250 Review: identify globe valve components

• [X1] INST260 Review: count sequentially in binary

• [X2] Build a circuit to sense pressure or vacuum using a differential pressure transmitter

• [X2] Calculate weight, density, or volume given the other two variables

• [X2] Calculate ranges for hydrostatic level-measuring instruments (∆P)

• [X2] Calculate calibration tensions for displacer-style level transmitters

• [X2] Identify suitability of basic level-measuring instruments to different processes

• [X2] Calculate instrument calibration points given ranges

• [X2] INST250 Review: match different control valve names with their P&ID symbols

• [X2] INST260 Review: explain basic network arbitration methods (e.g. CSMA/CD. master/slave. tokenpassing, etc.)

3

• Proportional (graded on a percentage scale according to quality/quantity of fulfillment)• [P] Identify and use appropriate sources of information for independent learning• [L] Explain how to diagnose a hypothetical problem in a pressure measurement system• [L] Explain how to diagnose a hypothetical problem in a level measurement system• [L] Explain or demonstrate a principle relevant to a pressure measurement system• [L] Explain or demonstrate a principle relevant to a level measurement system• [L] Perform a basic math calculation relevant to a pressure measurmement system• [L] Perform a basic math calculation relevant to a level measurmement system• [L] Explain or demonstrate safety procedure or tool usage• [F] Convert between different pressure units• [F] Qualitative analysis of a deadweight tester• [F] Explain operation of manometer• [F] Explain operation of different pressure gauge types• [F] Determine response of Twin-T differential capacitance circuit to applied pressure• [F] Perform algebraic manipulation of the Ideal Gas Law equation• [F] Calculate voltages and currents in a series-parallel DC circuit• [F] Determine the consequence of a component fault in an opamp circuit• [F] Analyze a series-parallel DC circuit, both faulted and unfaulted• [F] Determine likelihood of different faults in a simple circuit• [F] Convert between different pressure units• [F] Analyze calibration adjustments in a force-balance pneumatic ∆P transmitter• [F] Determine pressures in a three-valve manifold during maintenance• [F] Calculate instrument inputs and outputs for various conditions• [F] Analyze simple strain gauge circuit• [F] Perform algebraic manipulation of a fractional equation• [F] Perform simple trigonometric calculations• [F] Calculate voltages between different sets of points among several sources• [F] Sketch a circuit diagram for a simple 4-20 mA instrument loop• [F] Diagnose a problem in a multi-element electric heater circuit• [F] Qualitatively determine gas pressure inside heated vessels• [F] Determine likelihood of potential faults in a DP level measurement system• [F] Calculate voltage drops in a loop-powered level transmitter circuit• [F] Calculate ranges for instruments with remote seals• [F] Explain operation of a dip-tube densitometer• [F] Perform algebraic manipulation of a non-linear equation (satellite orbit velocity)• [F] Identify proper oscilloscope control functions• [F] Analyze a simple one-transistor amplifier circuit• [F] Sketch a circuit diagram for a simple relay circuit• [F] Diagnose a problem in a time-delay motor control circuit• [F] Calculate parameters associated with a guided-wave radar instrument• [F] Determine effects of process vapors on a capacitive level probe• [F] Describe different methods for measuring liquid interfaces• [F] Describe the purpose of a stilling well• [F] Analyze a strain-gauge bridge circuit• [F] Perform algebraic manipulation of a the Hall effect equation• [F] Perform algebraic manipulation of a fractional equation• [F] Calculate voltages between different sets of points among several sources• [F] Sketch a circuit diagram for a simple 4-20 mA instrument loop• [F] Diagnose a problem in a time-delay motor control circuit• [X1] Identify how to calibrate mechanical pressure gauges (link and lever mechanisms)• [X1] Identify different types of pressure switches and their operation• [X1] Identify and explain force- and motion-balance pressure-measuring instruments• [X1] Calculate complex pressure transmitter ranges

4

• [X1] Calculate electronic circuit parameters related to pressure measurement• [X2] Identify different types of level switches and their operation• [X2] Calculate liquid interface level transmitter ranges• [X2] Calculate complex buoyancy problems• [X2] Identify suitability of various level-measuring instruments to different processes• [X2] Calculate electronic circuit parameters related to level measurement

file INST240syllabus

5

Sequence of second-year Instrumentation courses

(or equivalent)

INST 200 -- 1 wk INST 205 -- 1 wk

GRADUATION !

Job Prep IIntro. to InstrumentationINST 206 -- 1 wk

Job Prep II

1st quarter 2nd quarter 3rd quarter

Pressure and LevelMeasurement

Measurement

MeasurementAnalytical

Temperature and Flow

INST 240 -- 4 wks

INST 241 -- 4 wks

Fal

l qu

arte

r

INST 242 -- 3 wks

Final ControlElements

Process Optimizationand Control Strategies

PID Controllersand Tuning

INST 250 -- 4 wks

INST 251 -- 4 wks

Win

ter

qu

arte

r

INST 252 -- 3 wks

Data AcquisitionSystems

Programmable LogicControllers

DCS and Fieldbus

INST 261 -- 4 wks

INST 262 -- 4 wks

Sp

rin

g q

uar

ter

INST 260 -- 3 wks

continuing students

(after completing all three quarters)

Core Electronics -- 1 year

file sequence

6

General student expectations

(Punctuality) You are expected to arrive at school on time (by 8:00 AM) every day. One late arrivalis permitted during the timespan of each sequential course (e.g. INST240, INST241, etc.) with no gradededuction. The grade deduction rate for late arrivals is 1% per incident.

(Attendance) You are expected to attend all day, every day. Each student has 12 “sick hours” per quarterapplicable to absences not verifiably employment-related, school-related, or weather-related. The gradededuction rate is 1% per hour of absence in any course. Each student must confer with the instructor toapply “sick hours” to any missed time – this is not done automatically for the student. Students may donateunused “sick hours” to whomever they specifically choose. You should contact your instructor and teammembers immediately if you know you will be late or absent. Absence on an exam day will result in a failinggrade for that exam, unless due to a documented emergency. Exams may be taken in advance for full credit.

(Participation) You are expected to participate fully in all aspects of the learning process includingindependent study, lab project completion, and classroom activities. It is solely your responsibility to catchup on all information missed due to absence. Furthermore, you shall not interfere with the participation ofothers in the learning process.

(Teamwork) You will work in instructor-assigned teams to complete lab assignments. Team membershipis determined by accumulated attendance and punctuality scores: students with similar participatory trendsare teamed together. Any student compromising team performance through frequent absence, habitualtardiness, or other disruptive behavior(s) will be expelled from their team and required to complete alllabwork independently for the remainder of the quarter.

(Preparation for theory sessions) You must dedicate at least 2 hours each day for reading assignmentsand homework questions to prepare yourself for theory sessions, where you will actively contribute your newknowledge. Graded quizzes and/or work inspections during each theory session will gauge your independentlearning. If absent, you may receive credit by having your preparatory work thoroughly reviewed prior tothe absence, or passing a comparable quiz after the absence.

(Feedback questions) You must complete and submit feedback questions for each section by the specifieddeadline. These are graded for accuracy and recorded as a “feedback” score. Plagiarism (presenting anyoneelse’s work as you own) in your answers will result in a zero score. It is okay to help one another learn thematerial, and to learn from outside sources, but your explanations must be phrased in your own words andwith your own work shown.

(Disciplinary action and instructor authority) The Student Code of Conduct (WashingtonAdministrative Codes WAC 495B-120) explicitly authorizes disciplinary action against the following typesof misconduct: academic dishonesty (e.g. cheating, plagiarism), dangerous or lewd behavior, harassment,intoxication, destruction of property, and/or disruption of the learning environment. Furthermore, the Codestates “Instructors have the authority to take whatever summary actions may be necessary to maintain orderand proper conduct in the classroom and to maintain the effective cooperation of the class in fulfilling theobjectives of the course.” Distractive or disruptive behavior such as (but not limited to) unauthorizedtelephone or computer use, disrespectful comments, sleeping, and conversation that either impede yourparticipation or the participation of others may result in temporary dismissal from class with attendancehours deducted.

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General grading and evaluation standards

Assessment criteria

• Mastery (all must be mastered – constitutes first 50% of course grade)• Mastery section of each lab exercise (unlimited attempts)• Mastery section of each exam including the hands-on circuit building or troubleshooting activity (up to

two attempts per sitting; up to three sittings); or mastery capstone assessment (unlimited attempts)

• Proportional (grades based on quality of fulfillment, counts toward last 50% of course grade)• Labwork, consisting of questions answered in an oral and demonstrative format (10% of grade)• Proportional section of all exams (20% of grade)• Feedback questions for all sections (20% of grade)• Daily quizzes demonstrating preparation for theory sessions (-1% per failed quiz)• Daily punctuality (-1% per incident of tardiness)• Attendance (-1% per hour past allotted “sick time”)• Destroyed items (-10% per incident) or purchase and replacement of the damaged item – This regards

avoidable incidents due to personal carelessness. When in doubt, ask the instructor how to properlyuse a tool or piece of equipment!

• Repaired instruments (+5% per item) – Instrument identified in need of repair by the instructor

Negative weighting represent objectives where 100% passing is a basic expectation (passing every quiz,punctuality every day, no accidents, etc.). Perfectly meeting these expectations does not count toward yourgrade, but failing to meet these basic expectations will result in grade loss.

Grading scaleAll grades are criterion-referenced (i.e. no grading on a “curve”)

• 100% ≥ A ≥ 95% 95% > A- ≥ 90%• 90% > B+ ≥ 86% 86% > B ≥ 83% 83% > B- ≥ 80%• 80% > C+ ≥ 76% 76% > C ≥ 73% 73% > C- ≥ 70% (minimum passing course grade)• 70% > D+ ≥ 66% 66% > D ≥ 63% 63% > D- ≥ 60% 60% > F

The proportional section of an exam may be taken only after taking the mastery section. Failing themastery exam will result in a 50% deduction from the proportional exam score, and you get a maximum oftwo re-takes to pass the mastery which must occur within three school days of the first attempt. Failure topass the mastery within three sittings will result in a failing grade for the course. Absence on a scheduledexam day will result in a 0% score for the proportional exam unless you provide documented evidence of anunavoidable emergency. You may receive half-credit on missed proportional exam questions after grading byexplaining your original mistake(s) and providing completely corrected responses on the first attempt.

If any other “mastery” objectives are not completed by their specified deadlines, your overall gradefor the course will be capped at 70% (C- grade), and you will have one more course day to complete theunfinished objectives. Failure to complete those mastery objectives by the end of that extra day (except inthe case of documented, unavoidable emergencies) will result in a failing grade (F) for the course.

Answers to “feedback questions” are due at the end of each course section. Full credit is given foreach question correctly and thoroughly answered, half credit for each question either not fully answeredor containing minor errors, and zero credit for major conceptual errors. Late submissions will receive zerocredit, unless due to a documented emergency.

“Lab questions” are assessed in a group format where students take turns answering questions from thelist at the instructor’s prompting. Grading follows the same rubric as for feedback questions: full creditfor thorough, correct answers; half credit for partially correct answers, and zero credit for major conceptualerrors. If you are absent during this assessment, you must submit written answers to all of the lab questions,which will be graded by the instructor.

file grading

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General tool and supply list

Wrenches• Combination (box- and open-end) wrench set, 1/4” to 3/4” – the most important wrench sizes are 7/16”,

1/2”, 9/16”, and 5/8”; get these immediately!• Miniature combination wrench set, 3/32” to 1/4”• Adjustable wrench, 6” handle• Hex wrench (“Allen” wrench) set, fractional – 1/16” to 3/8”

Note: when turning a bolt, nut, or tube fitting with a hexagonal body, the preferred ranking of handtools to use (from first to last) is box-end wrench or socket, open-end wrench, and finally adjustable wrench.Pliers should never be used to turn the head of a fitting or fastener unless it is absolutely unavoidable!

Pliers• Needle-nose pliers• Slip-joint pliers• Diagonal wire cutters

Screwdrivers• Slotted, 1/8” and 1/4” shaft• Phillips, #1 and #2• Jeweler’s screwdriver set

Measurement tools• Tape measure. 12 feet minimum• Vernier calipers, plastic okay

Electrical• Multimeter, Fluke model 87-IV or better• Wire strippers/terminal crimpers with a range including 10 AWG to 18 AWG wire• Soldering iron, 10 to 25 watt• Rosin-core solder• Package of compression-style fork terminals (e.g. Thomas & Betts “Sta-Kon” part number 14RB-10F,

14 to 18 AWG wire size, #10 stud size)

Safety• Safety glasses or goggles (available at BTC bookstore)• Earplugs (available at BTC bookstore)

Miscellaneous• Teflon pipe tape• Utility knife

You are recommended to engrave your name or place some other form of identifying mark on your tools,as you will be doing a lot of your work in teams, and it is easy to get tools mixed up. Also, lost tools getreturned to their owners much faster when they are marked!

An inexpensive source of high-quality tools is your local pawn shop. Look for name-brand tools withunlimited lifetime guarantees (e.g. Sears “Craftsman” brand, Snap-On, etc.).

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Methods of instruction

This course develops self-instructional and diagnostic skills by placing students in situations where theyare required to research and think independently. In all portions of the curriculum, the goal is to avoid apassive learning environment, favoring instead active engagement of the learner through reading, reflection,problem-solving, and experimental activities. The curriculum may be roughly divided into two portions:theory and practical.

TheoryIn the theory portion of each course, students independently research subjects prior to entering the

classroom for discussion. At the start of the classroom session, the instructor will check each student’spreparation using one of several methods (direct inspection of work, a pop quiz, targeted questions, etc.).Students then spend some class time working in small groups coordinating their presentations. The rest ofthe class time is spent interacting Socratically with the instructor in a large-group dialogue. The instructorcalls students (or student groups) to present what they found in their research, questions that arose duringtheir study, their solutions to problems, and any problem-solving techniques applied. The instructor’s roleis to help students take the information gleaned from their research and convert this into understanding.

LabIn the lab portion of each course, students work in teams to install, configure, document, calibrate, and

troubleshoot working instrument loop systems. Each lab exercise focuses on a different type of instrument,with a eight-day period typically allotted for completion. An ordinary lab session might look like this:

(1) Start of practical (lab) session: announcements and planning(a) Instructor makes general announcements to all students(b) Instructor works with team to plan that day’s goals, making sure each team member has a clear

idea of what they should accomplish(2) Teams work on lab unit completion according to recommended schedule:

(First day) Select and bench-test instrument(s)(One day) Connect instrument(s) into a complete loop(One day) Each team member drafts their own loop documentation, inspection done as a team (withinstructor)(One or two days) Each team member calibrates/configures the instrument(s)(Remaining days, up to last) Each team member troubleshoots the instrument loop(Last day) All teams answer lab questions, one team at a time, with the instructor

(3) End of practical (lab) session: debriefing where each team reports on their work to the whole class

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Distance delivery methods

Sometimes the demands of life prevent students from attending college 6 hours per day. In such cases,there exist alternatives to the normal 8:00 AM to 3:00 PM class/lab schedule, allowing students to completecoursework in non-traditional ways, at a “distance” from the college campus proper.

For such “distance” students, the same worksheets, lab activities, exams, and academic standards stillapply. Instead of working in small groups and in teams to complete theory and lab sections, though, studentsparticipating in an alternative fashion must do all the work themselves. Participation via teleconferencing,video- or audio-recorded small-group sessions, and such is encouraged and supported.

There is no recording of hours attended or tardiness for students participating in this manner. The paceof the course is likewise determined by the “distance” student. Experience has shown that it is a benefit for“distance” students to maintain the same pace as their on-campus classmates whenever possible.

In lieu of small-group activities and class discussions, comprehension of the theory portion of each coursewill be ensured by completing and submitting detailed answers for all worksheet questions, not just passingdaily quizzes as is the standard for conventional students. The instructor will discuss any incomplete and/orincorrect worksheet answers with the student, and ask that those questions be re-answered by the studentto correct any misunderstandings before moving on.

Labwork is perhaps the most difficult portion of the curriculum for a “distance” student to complete,since the equipment used in Instrumentation is typically too large and expensive to leave the school labfacility. “Distance” students must find a way to complete the required lab activities, either by arrangingtime in the school lab facility and/or completing activities on equivalent equipment outside of school (e.g.at their place of employment, if applicable). Labwork completed outside of school must be validated by asupervisor and/or documented via photograph or videorecording.

Conventional students may opt to switch to “distance” mode at any time. This has proven to be abenefit to students whose lives are disrupted by catastrophic events. Likewise, “distance” students mayswitch back to conventional mode if and when their schedules permit. Although the existence of alternativemodes of student participation is a great benefit for students with challenging schedules, it requires a greaterinvestment of time and a greater level of self-discipline than the traditional mode where the student attendsschool for 6 hours every day. No student should consider the “distance” mode of learning a way to havemore free time to themselves, because they will actually spend more time engaged in the coursework thanif they attend school on a regular schedule. It exists merely for the sake of those who cannot attend duringregular school hours, as an alternative to course withdrawal.

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General advice for successful learning

Reserve a time and a place for study• Schedule a block of time every day for study and make it a priority!• Create or join a study group, and help each other commit to regular study time.• Keep the environment of your study place ideal: whatever music (or no music) helps you concentrate,

whatever time allows for the least number of distractions, etc.• Plan to arrive at school at least a half-hour early and use the time to study as opposed to studying late

at night. This also helps guard against tardiness in the event of unexpected delays, and ensures you abetter parking space!

Who to study with• Classmates with similar schedules.• Classmates who are serious about their education.• Note that the intelligence of your study partners is not a significant criterion!

How to make time for study• Rid yourself of unnecessary, time-wasting gadgets: televisions, video games, mobile phones, etc. I am

not kidding!• Avoid recreational use of the internet.• Bring a meal to school every day and use your one-hour lunch break for study instead of eating out.• Carefully plan your lab sessions with your teammates to reserve a portion of each day’s lab time for

study.• Cut off all unhealthy personal relationships.

Make efficient use of the time you have• Do not procrastinate, waiting until the last minute to do something.• Don’t let small chunks of time at home or at school go to waste. Work a little bit on assignments during

these times.• Identify menial chores you can do simultaneously (e.g. house cleaning and laundry), and plan your

chore time accordingly to free up more time at home.

Take responsibility for your learning and your life• Obtain all the required books, and any supplementary study materials available to you. If the books

cost too much, look on the internet for used texts (www.amazon.com, www.half.com, etc.) and use themoney from the sale of your television and video games to buy them!

• Make an honest attempt to solve problems before asking someone else to help you. Being able toproblem-solve is a skill that will improve only if you continue to do work at it.

• If you detect trouble understanding a basic concept, seek clarification on it immediately. Never ignorean area of confusion, believing you will pick up on it later. Later may be too late!

• Do not wait for others to do things for you. No one is going to make extra effort purely on your behalf.• Seek help for any addictions. Addictions won’t just destroy your chance at an education – they can

destroy your whole life!

. . . And the number one tip for success . . .• Realize that there are no shortcuts to learning. Every time you seek a shortcut, you are actually cheating

yourself out of a learning opportunity!!

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12

Creative Commons License

This worksheet is licensed under the Creative Commons Attribution License, version 1.0. To viewa copy of this license, visit http://creativecommons.org/licenses/by/1.0/ or send a letter to CreativeCommons, 559 Nathan Abbott Way, Stanford, California 94305, USA. The terms and conditions of thislicense allow for free copying, distribution, and/or modification of all licensed works by the general public.

Simple explanation of Attribution License:

The licensor (Tony Kuphaldt) permits others to copy, distribute, display, and otherwise use thiswork. In return, licensees must give the original author(s) credit. For the full license text, please visithttp://creativecommons.org/licenses/by/1.0/ on the internet.

More detailed explanation of Attribution License:

Under the terms and conditions of the Creative Commons Attribution License, you may make freelyuse, make copies, and even modify these worksheets (and the individual “source” files comprising them)without having to ask me (the author and licensor) for permission. The one thing you must do is properlycredit my original authorship. Basically, this protects my efforts against plagiarism without hindering theend-user as would normally be the case under full copyright protection. This gives educators a great dealof freedom in how they might adapt my learning materials to their unique needs, removing all financial andlegal barriers which would normally hinder if not prevent creative use.

Nothing in the License prohibits the sale of original or adapted materials by others. You are free tocopy what I have created, modify them if you please (or not), and then sell them at any price. Once again,the only catch is that you must give proper credit to myself as the original author and licensor. Given thatthese worksheets will be continually made available on the internet for free download, though, few peoplewill pay for what you are selling unless you have somehow added value.

Nothing in the License prohibits the application of a more restrictive license (or no license at all) toderivative works. This means you can add your own content to that which I have made, and then exercisefull copyright restriction over the new (derivative) work, choosing not to release your additions under thesame free and open terms. An example of where you might wish to do this is if you are a teacher who desiresto add a detailed “answer key” for your own benefit but not to make this answer key available to anyoneelse (e.g. students).

Note: the text on this page is not a license. It is simply a handy reference for understanding the LegalCode (the full license) - it is a human-readable expression of some of its key terms. Think of it as theuser-friendly interface to the Legal Code beneath. This simple explanation itself has no legal value, and itscontents do not appear in the actual license.

file license

13

Metric prefixes and conversion constants

• Metric prefixes

• Yotta = 1024 Symbol: Y

• Zeta = 1021 Symbol: Z

• Exa = 1018 Symbol: E

• Peta = 1015 Symbol: P

• Tera = 1012 Symbol: T

• Giga = 109 Symbol: G

• Mega = 106 Symbol: M

• Kilo = 103 Symbol: k

• Hecto = 102 Symbol: h

• Deca = 101 Symbol: da

• Deci = 10−1 Symbol: d

• Centi = 10−2 Symbol: c

• Milli = 10−3 Symbol: m

• Micro = 10−6 Symbol: µ

• Nano = 10−9 Symbol: n

• Pico = 10−12 Symbol: p

• Femto = 10−15 Symbol: f

• Atto = 10−18 Symbol: a

• Zepto = 10−21 Symbol: z

• Yocto = 10−24 Symbol: y

1001031061091012 10-3 10-6 10-9 10-12(none)kilomegagigatera milli micro nano pico

kMGT m µ n p

10-210-1101102

deci centidecahectoh da d c

METRIC PREFIX SCALE

• Conversion formulae for temperature

• oF = (oC)(9/5) + 32

• oC = (oF - 32)(5/9)

• oR = oF + 459.67

• K = oC + 273.15

Conversion equivalencies for distance

1 inch (in) = 2.540000 centimeter (cm)

1 foot (ft) = 12 inches (in)

1 yard (yd) = 3 feet (ft)

1 mile (mi) = 5280 feet (ft)

14

Conversion equivalencies for volume

1 gallon (gal) = 231.0 cubic inches (in3) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl. oz.)= 3.7854 liters (l)

1 milliliter (ml) = 1 cubic centimeter (cm3)

Conversion equivalencies for velocity

1 mile per hour (mi/h) = 88 feet per minute (ft/m) = 1.46667 feet per second (ft/s) = 1.60934kilometer per hour (km/h) = 0.44704 meter per second (m/s) = 0.868976 knot (knot – international)

Conversion equivalencies for mass

1 pound (lbm) = 0.45359 kilogram (kg) = 0.031081 slugs

Conversion equivalencies for force

1 pound-force (lbf) = 4.44822 newton (N)

Conversion equivalencies for area

1 acre = 43560 square feet (ft2) = 4840 square yards (yd2) = 4046.86 square meters (m2)

Conversion equivalencies for common pressure units (either all gauge or all absolute)

1 pound per square inch (PSI) = 2.03602 inches of mercury (in. Hg) = 27.6799 inches of water (in.W.C.) = 6.894757 kilo-pascals (kPa) = 0.06894757 bar

1 bar = 100 kilo-pascals (kPa)

Conversion equivalencies for absolute pressure units (only)

1 atmosphere (Atm) = 14.7 pounds per square inch absolute (PSIA) = 101.325 kilo-pascals absolute(kPaA) = 1.01325 bar (bar) = 760 millimeters of mercury absolute (mmHgA) = 760 torr (torr)

Conversion equivalencies for energy or work

1 british thermal unit (Btu – “International Table”) = 251.996 calories (cal – “International Table”)= 1055.06 joules (J) = 1055.06 watt-seconds (W-s) = 0.293071 watt-hour (W-hr) = 1.05506 x 1010

ergs (erg) = 778.169 foot-pound-force (ft-lbf)

Conversion equivalencies for power

1 horsepower (hp – 550 ft-lbf/s) = 745.7 watts (W) = 2544.43 british thermal units per hour(Btu/hr) = 0.0760181 boiler horsepower (hp – boiler)

Acceleration of gravity (free fall), Earth standard

9.806650 meters per second per second (m/s2) = 32.1740 feet per second per second (ft/s2)

15

Physical constants

Speed of light in a vacuum (c) = 2.9979 × 108 meters per second (m/s) = 186,281 miles per second(mi/s)

Avogadro’s number (NA) = 6.022 × 1023 per mole (mol−1)

Electronic charge (e) = 1.602 × 10−19 Coulomb (C)

Boltzmann’s constant (k) = 1.38 × 10−23 Joules per Kelvin (J/K)

Stefan-Boltzmann constant (σ) = 5.67 × 10−8 Watts per square meter-Kelvin4 (W/m2·K4)

Molar gas constant (R) = 8.314 Joules per mole-Kelvin (J/mol-K)

Properties of Water

Freezing point at sea level = 32oF = 0oC

Boiling point at sea level = 212oF = 100oC

Density of water at 4oC = 1000 kg/m3 = 1 g/cm3 = 1 kg/liter = 62.428 lb/ft3 = 1.94 slugs/ft3

Specific heat of water at 14oC = 1.00002 calories/g·oC = 1 BTU/lb·oF = 4.1869 Joules/g·oC

Specific heat of ice ≈ 0.5 calories/g·oC

Specific heat of steam ≈ 0.48 calories/g·oC

Absolute viscosity of water at 20oC = 1.0019 centipoise (cp) = 0.0010019 Pascal-seconds (Pa·s)

Surface tension of water (in contact with air) at 18oC = 73.05 dynes/cm

pH of pure water at 25o C = 7.0 (pH scale = 0 to 14)

Properties of Dry Air at sea level

Density of dry air at 20oC and 760 torr = 1.204 mg/cm3 = 1.204 kg/m3 = 0.075 lb/ft3 = 0.00235slugs/ft3

Absolute viscosity of dry air at 20oC and 760 torr = 0.018 centipoise (cp) = 1.8 × 10−5 Pascal-seconds (Pa·s)

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16

Question 0

How to read actively:

• Make notes in a notebook while reading – if you’re not “reading with a pencil,” you’re not activelyreading! “Shorthand” notation, diagrams, and other notes jotted in a notebook are more effective atprompting active reading than underlining, highlighting, or otherwise marking up the original text.

• Mentally summarize each new concept or application you encounter in your own words before movingon to the next. If you cannot do this, you know you need to re-read the relevant sections until you can!

• Try to link new concepts to previously-learned concepts, and imagine how new concepts might apply toapplications not mentioned in the text. Make notes on these points so you may raise them as questionsduring class time.

• Note page numbers where important concepts, equations, images, tables, and problem-solving techniquesare introduced This will help you locate these important references during class time when you willcontribute in the dicsussion (“On page 572 it shows . . .”).

• Note page numbers of any sections in the reading that confound you, so you may call attention to it atthe start of class time to get help from classmates and/or the instructor.

• If the text demonstrates a mathematical calculation, such as how to apply a new equation to solving aproblem, pick up your calculator and work through the example as you read! Applications of math arean ideal opportunity to actively read a technical book, actually engaging in the material rather thanpassively observing what it says.

• Reserve the front pages of your notebook (or keep a separate notebook) for all mathematical formulaeyou come across in your reading. Briefly explain in your own words what each formula does and whatits terms mean.

Problem-solving techniques

• Clearly identify all “given” information, and also what the question is asking you to determine or solve.

• Sketch a diagram or graph to organize all the “given” information and show where the answer will fit.

• Performing “thought experiments” to visualize the effects of different conditions.

• Working “backward” from a hypothetical solution to a new set of given conditions.

• Changing the problem to make it simpler, and then solving the simplified problem (e.g. changingquantitative to qualitative, or visa-versa; substituting different numerical values to make them easierto work with; eliminating confusing details; adding details to eliminate unknowns; considering limitingcases that are easier to grasp).

• Identify any “first principles” of science, electronics, and/or instrumentation (e.g. Conservation laws,Feedback, Zero and Span, Ohm’s Law, etc.) that might apply to the question.

• Specifically identify which portion(s) of the question you find most confusing and need help with. Themore specific you are able to be, the better.

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17

Questions

Question 1

A group of mechanics are trying to figure out a solution to a problem. They are trying to remove thelid from a large metal vessel, but the lid is stuck and will not come off. Several of the mechanics try to usepry-bars to lift the lid, but to no avail. Others try to heat the lid with oxygen-acetylene torches and thenpry while it’s hot, but this does not budge the lid either.

Finally, one of the mechanics decides to plug all the pipe holes exiting this vessel except for one, thenconnect a water supply hose to that last pipe hole and use water pressure to force the lid off. After doingthis, the lid comes off quite easily.

Explain why the last mechanic’s solution worked, addressing the following points in your explanation:

• What is pressure?• How much force will a fluid such as water exert on a surface, given a certain fluid pressure?• Why was it prudent for the mechanic to use pressurized water and not compressed air to force the lid

off?

file i00018

Question 2

Read and outline the “Pressure” subsection of the “Fluid Mechanics” section of the “Physics” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03894

Question 3

Read and outline the “Pascal’s Principle and hydrostatic pressure” subsection of the “Fluid Mechanics”section of the “Physics” chapter in your Lessons In Industrial Instrumentation textbook. Note the pagenumbers where important illustrations, photographs, equations, tables, and other relevant details are found.Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored inthis reading.

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18

Question 4

In this hydraulic system, a force of 25 pounds is applied to the small piston (area = 10 in2). How muchforce will be generated at the large piston (area = 40 in2)? Also, calculate the fluid’s pressure.

10 in2 40 in2

Fluid

25 lb Force = ???

Finally, explain how Pascal’s Principle relates to this scenario.

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19

Question 5

A pressure calibration device called a deadweight tester generates very precise pressures by means ofcalibrated weights placed on top of a hydraulic piston:

weight

Primary piston

Secondary piston

oil

Gauge to becalibrated

Deadweight tester

The secondary piston is moved in and out by turning a handle on a threaded rod. Its sole purposeis to displace enough oil to force the primary piston to rise from its resting position, so that it is entirelysuspended by oil pressure. In that condition, the gauge will be subject to whatever pressure is proportionalto the weights placed on top of the primary piston, and the area of the primary piston.

What will happen to the gauge’s indication if the secondary piston is pushed in further? What willhappen to the gauge’s indication if the secondary piston is pulled out, but not so far that the primary pistoncomes down to its resting position? In other words, what effect does the secondary piston position have onpressure applied to the gauge?

weight

oil

weight

oil

Secondary pistonmoved out

Primary pistonmoves down

Secondary pistonmoved in

Primary pistonmoves up

In each condition, what happens to the gauge’s indication?Does the applied pressure increase, decrease, or stay the same?

??????

file i00153

Question 6

Read and outline the “Manometers” subsection of the “Fluid Mechanics” section of the “Physics”chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers where importantillustrations, photographs, equations, tables, and other relevant details are found. Prepare to thoughtfullydiscuss with your instructor and classmates the concepts and examples explored in this reading.

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Question 7

Read and outline the “Systems of Pressure Measurement” subsection of the “Fluid Mechanics” sectionof the “Physics” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numberswhere important illustrations, photographs, equations, tables, and other relevant details are found. Prepareto thoughtfully discuss with your instructor and classmates the concepts and examples explored in thisreading.

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Question 8

Read the “Systems of Pressure Measurement” subsection of the “Fluid Mechanics” section of the“Physics” chapter in your Lessons In Industrial Instrumentation textbook, particularly how to use fractionsfor cancellation of units, and how to manage conversions between units of pressure measurement that do notshare the same zero point. Then, use that same mathematical technique to convert between the followingunits of pressure:

• 25 PSI = ??? kPa

• 40 ”W.C. = ??? PSI

• 5.60 bar (gauge) = ??? PSI

• 3 atm = ??? PSIA

• 1,200 ”Hg = ??? ”W.C.

• 12 feet W.C. = ??? PSI

• 4 PSI vacuum = ??? PSIA

• 110 kPa = ??? ”W.C.

• 982 mm Hg = ??? ”Hg

• 50 Pa = ??? PSI

• 21 atm = ??? ”Hg absolute

• 270 PSIG = ??? atm

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21

Question 9

Calculate the amount of force generated by this hydraulic ram for the given pressures, assuming acircular piston with a diameter of 5 inches:

piston

rod

5"

Fluid pressure

(vented)

• P = 260 PSI F =

• P = 1100 PSI F =

• P = 461 kPa F =

• P = 399 ”W.C. F =

• P = 2.77 bar F =

file i04179

Question 10

Read selected portions of the National Transportation Safety Board’s Pipeline Accident Report, PipelineRupture and Subsequent Fire in Bellingham, Washington, June 10, 1999 (Document NTSB/PAR-02/02 ;PB2002-916502).

Page 6 of the report shows a graphical trend of pipeline pressure before, during, and after the rupture.How high did the pressure spike, in units of PSI? Do you suppose this was PSIG or PSIA? Convert thismeasurement into units of kilopascals (kPa).

Based on what you see on the trend graph, was this pipeline carrying a gas or a liquid? How can youtell, from the shape of the trend alone?

Examine the photographs of the ruptured pipeline on page 41 of the report. Based on what you knowabout fluid pressure, determine where along the pipeline’s interior the force of the pressure was exerted.

Page 57 of the report discusses how the pipeline had been “hydrostatically tested” after its originalinstallation. This means it was pressure-tested with non-moving (static) water. Why was this detailimportant to the investigation?

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22

Question 11

A force of 50 pounds is applied longitudinally through a flat-ended steel rod 1/4 inch in diameter, pressingagainst a flat surface. An equal amount of force is applied longitudinally through a pointed center-punchtool, against the same flat surface.

50 lb

flat surface

50 lb

rod center-punch

pressure pressure

The two forces are equal. Are the two pressures equal as well? Explain.file i00141

Question 12

If force is exerted on the piston of this hydraulic cylinder, in what direction(s) will this force betransmitted to the cylinder walls? In other words, how does a fluid under pressure push against itssurrounding container?

Piston

Rod

Fluid

Force

Hydraulic cylinder

Steel cylinderwall

Steel cylinderwall

file i00142

23

Question 13

Suppose a small rubber ball is floating inside the fluid of a hydraulic cylinder as shown below. Whatwill happen to the ball when a pushing force is exerted on the cylinder’s rod? What will happen to the ballwhen a pulling force is exerted on the rod?

Rubber ball

file i00143

Question 14

Identify and distinguish between absolute pressure, gauge pressure, and differential pressure. Give atleast one example of each kind of pressure.

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Question 15

A scuba diver’s air tank contains 2,000 PSI of air, as measured by a pressure gauge before descendinginto the water. The diver descends 50 feet into the water, where the surrounding water pressure caused bythe water’s weight (called hydrostatic pressure) is approximately 22 PSI. Assuming that the diver consumesan inconsequential amount of air from the tank during the 50 foot descent, express the air pressure insidethe tank in terms of absolute pressure, gauge pressure, and differential pressure (the differential pressurebetween the tank and the surrounding hydrostatic pressure of the water).

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24

Question 16

A surface-mounted water pump pulls water out of a well by creating a vacuum, though it might be moretechnically accurate to say that the pump works by reducing pressure in the inlet pipe to a level less thanatmospheric pressure, allowing atmospheric pressure to then push water from the well up the pump’s inletpipe:

Pump

Water

Atmosphericpressure

Based on this description of pump operation, what is the theoretical maximum height that any pumpcan lift water out of a well? Hint: how much is the pressure of Earth’s atmosphere at sea level?

Domestic water wells may be hundreds of feet deep. How can water be pumped out of wells this deep,given the height limitation of vacuum pumping?

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25

Question 17

Water pressure available at a fire hydrant is 80 PSI. If a fire hose is connected to the hydrant and thehydrant valve opened, how high can the end of the hose be raised and still have water flow out the end?

80 PSI

How high???

Now, suppose that a spray nozzle attached to the end of the hose requires at least 30 PSI of pressureat the coupling in order to function properly. How high can the hose be raised then, and still have enoughwater pressure at the nozzle to allow for the fighting of a fire?

80 PSI

How high???

required hereAt least 30 PSI

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26

Question 18

Calculate the amount of force exerted by the fluid pressure in each of these scenarios:

Scenario #1A cube-shaped box, measuring 4 inches on a side, contains a gas at a pressure of 3 PSIG. How much

force does this pressure direct on each wall of the box?

Scenario #2An hydraulic cylinder has a 2 inch diameter piston. If the fluid pressure inside the cylinder is 1500 PSI,

how much force will be generated at the piston?

Scenario #3A 10-inch diameter piston is located at the bottom of a water column 4 feet high. How much force will

the hydrostatic pressure of the water create on the piston?

Water

piston

4 feet

10"

Force = ???

file i00149

Question 19

Complete the following table of equivalent pressures:

PSIG PSIA inches Hg (G) inches W.C. (G)18

40033

60452

121

-5

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27

Question 20

Question 21

Lightly read the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook to identify several different mechanical technologies for measuring pressure, thenbriefly describe the operating principle of each one:

• Manometers (identify some of the different types!)

• Bellows

• Diaphragm

• Bourdon tube (identify some of the different types!)

file i03899

Question 22

Lightly read the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook to identify different electronic technologies for measuring pressure, then brieflydescribe the operating principle of each one:

• Strain gauge (electronic sensing)

• Capacitance sensors (electronic sensing)

• Resonant sensors (electronic sensing)

file i03902

Question 23

Read and outline the “DP Transmitter Construction and Behavior” subsection of the “DifferentialPressure Transmitters” section of the “Continuous Pressure Measurement” chapter in your Lessons InIndustrial Instrumentation textbook. Note the page numbers where important illustrations, photographs,equations, tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructorand classmates the concepts and examples explored in this reading.

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Question 24

Read and outline the “DP Transmitter Applications” subsection of the “Differential PressureTransmitters” section of the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook. Note the page numbers where important illustrations, photographs, equations,tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructor andclassmates the concepts and examples explored in this reading.

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28

Question 25

How much pressure, in inches of water column, is being applied to this inclined water manometerto create a total displacement of 14 inches along the length of the tubes, inclined at angles of 20o fromhorizontal?

14"

20o

Appliedpressure

(vented)

Next, convert this pressure into units of kPa.file i00168

Question 26

Convert between the following units of pressure. Remember that any pressure unit not explicitly specifiedas either absolute (A) or differential (D) is to be considered gauge. Also, remember those units which alwaysrepresent absolute pressure, and have no need for a letter “A” suffix!

• 25 PSIA = ??? atm

• 340 ”W.C. = ??? PSIA

• 0.73 bar (gauge) = ??? ”Hg

• 5.5 atm = ??? torr

• 2,300 cm Hg = ??? ”W.C.A

• 500 m torr = ??? PSIA

• 91.2 cm W.C. = ??? kPa

• 110 kPa = ??? ”W.C.

• 620 mm HgA = ??? torr

• 77 Pa = ??? PSIA

• 1 atm = ??? ”W.C.A

• 270 PSIA = ??? atm

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29

Question 27

Read the “Systems of Pressure Measurement” subsection of the “Fluid Mechanics” section of the“Physics” chapter in your Lessons In Industrial Instrumentation textbook, particularly how to use fractionsfor cancellation of units, and how to manage conversions between units of pressure measurement that do notshare the same zero point. Then, use that same mathematical technique to convert between the followingunits of pressure:

• 5 PSI vacuum = ??? PSIA

• 25 ”Hg vacuum = ??? PSIA

• 2,800 µ torr = ??? PaA

• -59 ”W.C. = ??? torr

• 4,630 PaA = ??? PSI

• 0.05 atm = ??? ”W.C.

• -3 kPa = ??? atm

• 10 feet W.C. vacuum = ??? ”HgA

• 300 cm Hg = ??? atm

• -2 mm W.C. = ??? bar (absolute)

• 4 atm = ??? ”W.C.A

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Question 28

Explain what is wrong with this attempt to convert a gauge pressure of 65 PSI into units of atmospheres(atm):

(

65 PSI

1

)(

1 atm

14.7 PSI

)

= 4.422 atm

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30

Question 29

You are asked to install a pressure transmitter to measure the pressure on a process vessel. Plantoperations wants a transmitter to give an increasing signal in direct proportion to an increasing fluid pressurein the vessel. The vessel’s pressure ranges anywhere from atmospheric (0 PSI gauge) to 200 PSIG. Becausedifferential pressure transmitters (“DP cells”) are so commonplace in industry, and so versatile, you chooseto use one in this application.

Process vessel

H L

???

0 to 200 PSIG

However, the transmitter, being a differential pressure unit, has two pressure ports: one marked “high”and one marked “low.” The pressure vessel only has one tube connection on it for you to connect thetransmitter. Which port of the transmitter do you choose to connect to the vessel? What do you do withthe other port on the transmitter?

Now, suppose this process vessel contained a vacuum instead of a pressure greater than atmosphere,and operations personnel wanted the transmitter’s output signal to increase as the vacuum grows stronger.

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31

Question 30

A large water filter occasionally plugs with debris, and operations wants to have a gauge indicationof this plugging. Since plugging of the filter will result in greater differential pressure drop across it forany given amount of water flow through it, measuring pressure drop with a differential pressure gauge willprovide a simple indication of filter plugging.

Draw the connecting tubes between the differential pressure gauge and the filter (the two “taps” shownon the pipes are ready to connect to instrument tubing) so that the gauge registers more pressure as thefilter becomes more plugged:

Water filter

Waterin

Waterout

H L

Tap

Tap

Differential pressuregauge

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32

Question 31

2.036 inches of mercury (”Hg) is an equivalent pressure to 27.68 inches of water (”W.C. or ”H2O). Thisfact allows us to create a “unity fraction” from these two quantities for use in converting pressure units frominches mercury to inches water or visa-versa. Two examples are shown here:

(

310 ”Hg

1

)(

27.68 ”W.C.

2.036 ”Hg

)

= 4215 ”W.C.

(

45 ”W.C.

1

)(

2.036 ”Hg

27.68 ”W.C.

)

= 3.31 ”Hg

But what if we are performing a unit conversion where the initial pressure is given in inches of mercuryor inches of water absolute? Can we properly make a unity fraction with the quantities 2.036 ”HgA and27.68 ”W.C.A as in the following examples?

(

310 ”HgA

1

)(

27.68 ”W.C.A

2.036 ”HgA

)

= 4215 ”W.C.A

(

45 ”W.C.A

1

)(

2.036 ”HgA

27.68 ”W.C.A

)

= 3.31 ”HgA

Explain why or why not.file i02942

Question 32

How much pressure, in inches of water column, is being applied to this inclined water manometer todisplace water 5 inches along the length of the tube, inclined at an angle of 30o from horizontal? Assume anegligible change in liquid level inside the “well” throughout the measurement range of the instrument:

water

Appliedpressure

(vented)

5"

30oWell

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33

Question 33

A simple way to make a micromanometer (an extremely sensitive manometer) is to connect two large-diameter vertical tubes by a small-diameter, transparent tube with an air bubble in it. The air bubblebecomes the marker for reading pressure along a scale:

bubbleair

Scale

A simple micromanometer

Water

If both of the large vertical tubes are 2.5 inches in diameter, and the transparent, horizontal tube is0.25 inches in diameter, how much differential pressure will be indicated by 1 inch of horizontal bubbledisplacement? Assume the use of water for the manometer liquid.

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34

Question 34

A manometer may be used to measure differential pressure across a restriction placed within a pipe.Pressure will be dropped as a result of flow through the pipe, making the manometer capable of (indirectly)measuring flow:

Flow

Higherpressure

Lowerpressure

Mercury manometer

Pipe Restriction

In the example shown above, the fluid moving through the pipe is air, and the manometer uses mercuryas the indicating liquid. If we try to measure the flow rate of a liquid such as water using the same technique,though, we will find that the manometer does not register quite the way we might expect:

Higherpressure

Lowerpressure

Mercury manometer

Pipe Restriction

Flow

That is to say, given the exact same amount of differential pressure generated by the restriction, themanometer will register differently than if it was measuring air pressure. Determine whether the manometerwill register falsely high or falsely low, and also why it will do so.

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35

Question 35

In this hydraulic lift system, the oil pressure is registered by a pressure gauge as the vehicle is lifted offthe ground. The heavier the vehicle, of course, the more oil pressure will be required to lift it:

OilOil

Compressedair . . . from

aircompressorValve

Valve

Pressure gauge

We know that force is equal to pressure times area in a fluid system (F = PA), and from this relationshipwe could calculate how much force was being exerted by the lift in raising a vehicle off the ground for anygiven amount of oil pressure. For example, if we knew the hydraulic pressure was 350 PSI and the pistonarea was 13.7 square inches, we could calculate that the vehicle weighs 4795 pounds. It is important for unitcancellation in the F = PA formula that we know the pressure in units of lb/in2 and the area in units ofin2, otherwise the force would not come out in units of pounds:

F = PA

[lb] =

[

lb

in2

]

[

in2]

Suppose, though, we knew neither the area of the piston (A) nor the unit of pressure measurement(imagine a pressure gauge with numbers and divisions on the scale, but no unit written). We do know,however, that the pressure gauge needle rises to “37.2” when a 5000 pound vehicle is lifted off the ground.

You are asked to figure out a multiplying constant for mechanics to use when determining the weight ofa vehicle from the gauge’s indication. In other words, you need to calculate a number which when multipliedby the gauge’s reading will give vehicle weight in pounds.

In physics, this number is known as a constant of proportionality, and it is usually signified by the letterk. Knowing that force is proportional to pressure for a constant piston area, we can say that force is equalto some constant (k) multiplied by fluid pressure (P ):

F ∝ P

F = kP

Solve for k in this hydraulic lift system.

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36

Question 36

A very useful principle in physics is the Ideal Gas Law, so called because it relates pressure, volume,molecular quantity, and temperature of an ideal gas together in one neat mathematical expression:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Apply this law to the scenario of a gas-filled cylinder and movable piston:

Gas Cylinder

Piston

In particular, sketch how the gas pressure inside the cylinder relates to changes in cylinder volumecaused by piston movement, assuming no change in gas temperature or leakage of gas molecules from thecylinder:

P

V

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37

Question 37

Question 38

Question 39

Question 40

Question 41

Read and outline the “Zero and Span Adjustments (Analog Transmitters)” section of the “InstrumentCalibration” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers whereimportant illustrations, photographs, equations, tables, and other relevant details are found. Prepare tothoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading.

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Question 42

Read and outline the “Damping Adjustments” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

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Question 43

Read and outline the “LRV and URV Settings, Digital Trim (Digital Transmitters)” section of the“Instrument Calibration” chapter in your Lessons In Industrial Instrumentation textbook. Note the pagenumbers where important illustrations, photographs, equations, tables, and other relevant details are found.Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored inthis reading.

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Question 44

Read the “An Analogy for Calibration versus Ranging” section of the “Instrument Calibration”chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers where importantillustrations, photographs, equations, tables, and other relevant details are found. Prepare to thoughtfullydiscuss with your instructor and classmates the concepts and examples explored in this reading.

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Question 45

Read and outline the “Calibration Procedures” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

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Question 46

Read and outline the “Typical Calibration Errors” section of the “Instrument Calibration” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

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Question 47

Read and outline the “Instrument Turndown” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03909

Question 48

Read and outline the “NIST Traceability” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03910

Question 49

Shown here is a diagram of a standard pressure gauge, based on the pressure-sensing action of a hollow,C-shaped metal tube called a bourdon tube:

Appliedpressure

Pointer

Pressure gauge

Pinion gearSector gear

Link

Bourdontube

mechanism

(dots shownare pivot points)

Using arrows, trace the motions of all moving components in this mechanism as an increasing pressureis applied to the fitting at the bottom of the bourdon tube.

Also, describe how the measurement span of this pressure gauge could be changed. In other words,what would have to be moved, adjusted, or altered in this mechanism in order to change the proportionalityof applied pressure to pointer movement?

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39

Question 50

A pressure gauge is supposed to accurately indicate applied pressure over its full calibrated range. Inthis example, a gauge with a range of 0 to 500 PSI is subjected to five different pressures along that range,and its response is accurate at all those points:

0 500

250

125 375

0 500

250

125 375

0 500

250

125 375

0 PSI applied 125 PSI applied 250 PSI applied

0 500

250

125 375

0 500

250

125 375

375 PSI applied 500 PSI applied

Describe, by drawing a set of five meter readings such as the set shown above, how a pressure gaugeaccurate at 0% and 100% of applied pressure – but with a nonlinearity problem between the LRV and URVpoints – might respond to the same five applied pressures.

Furthermore, describe how a bourdon tube pressure gauge instrument might be adjusted for linearity.In other words, how may a nonlinear pressure gauge be calibrated to become more linear?

file i00174

Question 51

Answer the following four questions about deadweight testers:

(1) What is it about the nature of a deadweight tester that makes it so accurate and repeatable?To phrase this question in the negative, what would have to change in order to affect the accuracyof a deadweight tester’s output pressure?

(2) Why is it important for a deadweight tester to be level while it is being used to calibrate apressure instrument?

(3) What effect will trapped air have inside a deadweight tester?

(4) Why is it advisable to gently spin the primary piston and weights while the piston is suspendedby oil pressure?

file i00154

40

Question 52

A device called a manometer is a very simple and yet very precise pressure measuring instrument. Itworks on the principle of a differential pressure displacing a vertical liquid column. The distance betweenthe tops of the two liquid columns is proportional to the difference in pressure applied to tops of thetwo vertical tubes. This is where we get pressure units of “inches/centimeters of water column” and“inches/centimeters/millimeters of mercury” – from the operation of a manometer:

Appliedpressure(greater)

Appliedpressure(lesser)

HeadTransparenttube allows

liquid columnsto be seen

Manometer

Explain how this instrument may serve as a standard for pressure measurement, just as a deadweighttester may serve as a standard for pressure generation. To phrase this question in the negative, what wouldhave to change in order to affect the pressure measurement accuracy of a manometer?

file i00160

41

Question 53

A free-floating piston inside a hydraulic cylinder has a 1000 PSI of fluid pressure applied to one side ofthe piston, and 850 PSI of pressure applied to the other side of the piston. The piston itself is 2.75 inches indiameter. How much force will act on the piston, with these pressures applied to it?

850 PSI

1000 PSI

2.75"

piston

Force on piston ???

tubing

tubing

file i00155

Question 54

A double-acting hydraulic cylinder has 500 PSI of pressure applied to the side without the rod and 750PSI of pressure applied to the rod-side. Calculate the resultant force generated at the piston and transmittedthrough to the rod, and also determine this force’s direction. The piston is 5 inches in diameter, and therod is 1 inch in diameter.

piston

rod

5"

1"

750 PSI

500 PSI

Force ???

file i00156

42

Question 55

A very useful principle in physics is the Ideal Gas Law, so called because it relates pressure, volume,molecular quantity, and temperature of an ideal gas together in one neat mathematical expression:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Although this “law” is not perfectly accurate for real gases, especially at high pressures and/or near thepoint of liquefaction, it is quite accurate for air near ambient temperature and pressure.

One very practical application of this law is found in a method for generating low air pressures suchas those easily measured by water- or oil-based manometers. Most mechanical air compressors generatepressures far exceeding the range of all but the largest manometers. Though it is possible to purchaseprecision pressure regulators for reducing such large pressures down to a level measurable by a manometer,these devices are expensive. An alternative is to generate the air pressure with a hand pump (such as abicycle tire pump) connected to a relatively large pressure vessel:

Handpump

Pressurevessel

To instrumentunder test

Manometer

Vent

12

3

Without the volume of the pressure vessel connected to the tubing system, the air pressure wouldincrease dramatically for each stroke of the air pump. With the pressure vessel connected, each pump strokecontributes a much smaller amount of additional pressure to the system. Use the ideal gas law equation toexplain why this is.

file i00286

43

Question 56

One challenge technicians face when calibrating low-pressure instruments is how to generate very lowair pressures to simulate different low-pressure conditions for the pressure instrument under test. Measuringlow pressures is no problem at all: very simple manometers will do the job quite nicely. Most mechanical aircompressors, however, generate pressures far exceeding the range of most manometers. Though it is possibleto purchase precision pressure regulators for reducing such large pressures down to a level measurable by amanometer, these devices are expensive.

A simple way to “divide” the pressure output of a standard pressure regulator from a few PSI to a fewinches of water is to use a pair of small valves (preferably needle valves allowing for precise adjustment) tothrottle the flow of compressed air and vent the regulator’s output to atmosphere, then tap between thosevalves to obtain a reduced pressure:

Air compressor

Manometer

Receiver

Vent

To instrumentunder test

Pressureregulator

Complete the following schematic diagram showing an electrical model for this pneumatic system, andthen explain how it works:

To instrumentunder test

Low-rangevoltmeter+

−High voltage

source

3-terminalIC regulator

file i00287

44

Question 57

Suppose a pressure gauge uses a diaphragm as its pressure-sensing element, like this:

fulcrum

pivots

Scale

Pressure to bemeasured

pointer

spring

This mechanism will work, but what if we desired to make it more sensitive? That is, we wished todecrease its measurement span so that less pressure would drive the pointer to full-scale. What could wealter in this mechanism to decrease the measurement span?

file i00172

45

Question 58

Some bourdon tube gauges are equipped with a very small spiral spring attached to the pointer shaft:

Pointer

Link

spring

anchorpoint

Now, this spring is much too weak to have any detectable effect on the span of the gauge. In otherwords, it does not measurably resist the bending action of the bourdon tube, as a “range spring” would inanother design of instrument.

Given its weakness, what possible purpose does this spring serve in the gauge mechanism?

file i00175

Question 59

Describe what a spiral bourdon tube is, and what a helical bourdon tube is. Explain why these styles ofbourdon tubes are often used in precision pressure gauges, and what advantage(s) they have over C-shapedbourdon tubes.

file i00179

Question 60

46

Question 61

Shown here is a very simple pressure transmitter, a device that measures a fluid pressure and convertsthat measurement into an electrical signal:

Appliedpressure

Box

Thin, flexiblemetal diaphragm

+−10 V

Vout

Pressure transmitter

Powerterminals

Outputterminals

5 kΩPotentiometer

Suppose the potentiometer wiper will be at its full-down position with no pressure applied to thediaphragm, and will be at its full-up position with 15 PSI (15 pounds per square inch) of pressure applied tothe diaphragm. Based on this information, and what you see in the schematic diagram, answer the followingquestions:

• Lower Range Value (LRV) of input, in units of PSI:

• Upper Range Value (URV) of input, in units of PSI:

• Input span, in units of PSI:

• Lower Range Value (LRV) of output, in units of volts:

• Upper Range Value (URV) of output, in units of volts:

• Output span, in units of volts:

Now, suppose we make a modification to the electrical circuit portion of the pressure transmitter.Assume the diaphragm still responds to pressure and moves the potentiometer wiper the same way it didbefore. Answer the same questions again:

47

Appliedpressure

Box

Thin, flexiblemetal diaphragm

+−10 V

Vout

Pressure transmitter

Powerterminals

Outputterminals

5 kΩPotentiometer

1.25 kΩ

6.25 kΩ

• Lower Range Value (LRV) of input, in units of PSI:• Upper Range Value (URV) of input, in units of PSI:• Input span, in units of PSI:

• Lower Range Value (LRV) of output, in units of volts:• Upper Range Value (URV) of output, in units of volts:• Output span, in units of volts:

The latter design outputs what is commonly called a live-zero signal, whereas the first transmitteroutputs a dead-zero signal. Live-zero signals are much preferred in industrial instrumentation, because theymore readily betray wiring failures than dead-zero signals.

Explain how you answered all the questions, and also show currents and voltage drops in both circuits(complete with arrows showing directions of current). Then, elaborate on why you think live-zero signalsare preferable to dead-zero signals.

file i00083

48

Question 62

Read the product manual for the WIKA (brand) “DELTA-trans” (model 891-34-2189) differentialpressure transmitter, which uses a Hall Effect sensor to generate an electronic output signal from a senseddifferential pressure. Then, answer the following questions:

Explain how an applied pressure is sensed by this DP transmitter, and how the mechanical motion isconverted into an electronic signal. You may need to do some research on “Hall Effect” sensors in order tofully answer this question.

Identify how the zero and span adjustments are implemented – are they mechanical, or electrical?

Identify how the “high” and “low” ports of this DP instrument are labeled. Which way does the sensingelement move when a fluid pressure is applied to the “low” port?

file i03911

Question 63

Read and outline the “Piezoresistive (Strain Gauge) Sensors” subsection of the “Electrical PressureElements” section of the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook. Note the page numbers where important illustrations, photographs, equations,tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructor andclassmates the concepts and examples explored in this reading.

file i03912

Question 64

Read and outline the “Differential Capacitance Sensors” subsection of the “Electrical Pressure Elements”section of the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook. Note the page numbers where important illustrations, photographs, equations, tables, and otherrelevant details are found. Prepare to thoughtfully discuss with your instructor and classmates the conceptsand examples explored in this reading.

file i03913

Question 65

Read and outline the “Resonant Element Sensors” subsection of the “Electrical Pressure Elements”section of the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook. Note the page numbers where important illustrations, photographs, equations, tables, and otherrelevant details are found. Prepare to thoughtfully discuss with your instructor and classmates the conceptsand examples explored in this reading.

file i03914

Question 66

Locate the “Ordering Information” page for the Rosemount model 3051S Series differential pressuretransmitter, located in the Product Data Sheet document (00813-0100-4801 Revision GA, April 2006) onpage 27. Then, answer the following questions:

Identify the different “performance classes” for this instrument model. Specifically, identify thepercentage accuracy and the rangedown limits for each.

Identify some of the different codes for pressure measurement ranges. What is the lowest pressuremeasurement range you can order this instrument in? What is the highest pressure measurement range?

Identify some of the different isolating diaphragm materials available for this instrument.file i03915

49

Question 67

A strain gauge is a device used to measure the strain (compression or expansion) of a solid object byproducing a resistance change proportional to the amount of strain. As the gauge is strained, its electricalresistance alters slightly:

Straingauge

(glued to specimen)

Metal specimenApplied force Applied force

Change in R

Explain why the electrical resistance of a strain gauge changes as it stretches and shrinks, and alsocorrelate the direction of resistance change (more or less) with the direction of applied force.

The following strain gauge is shown connected in a “quarter-bridge” circuit (meaning only one-quarterof the bridge actively senses strain, while the other three-quarters of the bridge are fixed in resistance):

Metalspecimen

Straingauge

(glued to specimen)

VA B

Explain what would happen to the voltage measured across this bridge circuit (VAB) if the strain gaugewere to be compressed, assuming that the bridge begins in a balanced condition with no strain on the gauge.

file i00181

50

Question 68

The following bridge circuit uses two strain gauges (one to measure strain, the other to compensatefor temperature changes), the amount of strain indicated by the voltmeter in the center of the bridge.Unfortunately, though, it has a problem. Instead of registering a very small voltage as it normally does, thevoltmeter shows a large voltage difference, with point B positive and point A negative:

Straingauge

VA B

"Dummy"gauge

R1 R2

Abnormally large voltage

Something is wrong in the bridge circuit, because this voltage is present even when there is no physicalstress on the specimen. Identify which of the following faults could cause the excessive voltage to appearacross the voltmeter, and which could not. Consider only one of these faults at a time (no multiple,simultaneous faults):

• Resistor R1 failed open• Resistor R1 failed shorted• Resistor R2 failed open• Resistor R2 failed shorted• Strain gauge (measurement) failed open• Strain gauge (measurement) failed shorted• “Dummy” gauge (temperature compensation) failed open• “Dummy” gauge (temperature compensation) failed shorted• Voltage source is dead (no voltage output at all)

file i00188

51

Question 69

Convert between the following units of pressure:

• 22 PSI = ??? PSIA

• 13 kPa = ??? ”W.C.

• 81 kPa = ??? PSI

• 5 atm = ??? PSIA

• 200 ”Hg = ??? ”W.C.

• 17 feet W.C. = ??? ”Hg

• 8 PSI vacuum = ??? PSIA

• 900 Torr = ??? ”W.C.A

• 300 mm Hg = ??? PSI

• 250 ”W.C. = ??? bar (gauge)

• 70 ”W.C. = ??? ”Hg

• 300 PSIG = ??? atm

file i00226

Question 70

Complete the following table of equivalent pressures:

Atm PSIG inches W.C. (G) PSIA3.5

818834

07.12

3682

100

file i02939

52

Question 71

Explain how the strain gauge acts to sense pressure:

Diaphragm

Appliedpressure

Box

Vent

Straingauge

Metalbar

Outputterminals

Now, explain how this simple instrument could be modified to measure differential pressure.file i00182

53

Question 72

A simple form of electronic pressure transmitter could be made with a bourdon tube and a LinearVariable Differential Transformer, or LVDT:

Appliedpressure

Bourdontube

Outputterminals

Movablecore

Explain how this instrument works, what type of electrical output signal it generates (e.g. current,voltage, resistance, etc.), and what polarity (if any) that output signal has.

file i00183

54

Question 73

A simple form of electronic pressure transmitter could be made with a bourdon tube and a differentialcapacitor:

Appliedpressure

Bourdontube

Movabledielectric Output

terminals

Explain how this instrument works, what type of electrical output signal it generates (e.g. current,voltage, resistance, etc.), and what polarity (if any) that output signal has.

file i00184

55

Question 74

Most modern electronic differential pressure instruments use a differential capacitance pressure-sensing“capsule” to detect applied pressure and convert that measurement into an electrical quantity:

Sensingdiaphragm

Isolatingdiaphragmdiaphragm

Isolating

Siliconefill fluid

Pressure Pressure

Solid metal

Output terminals

The Rosemount models 1151 and 3051 differential pressure transmitters are popular examples of thistechnology.

Explain how this type of pressure sensor works, and what type of circuit it would be connected to inorder to convert the variable capacitance into either a voltage or a current signal.

file i00185

56

Question 75

An ingenious circuit used to convert the output of a differential capacitance sensor into a DC voltagesignal is the diode twin-t circuit shown here:

C C’

Vout

R

R

Rload

D

D

The AC “excitation” voltage source is typically of high frequency, at least 1 MHz. The diodes arefast-switching units, ideally Schottky diodes. Resistors R must be equal in value, but Rload is usually muchgreater than R. Together, the two matched resistors (R) form an averaging network for the two capacitancesC and C ′ as they alternately discharge through Rload.

Identify which capacitance (C or C ′) must increase in value to generate a positive DC output voltage,and why this is so.

file i00186

Question 76

As any musician who plays a stringed instrument knows, the resonant frequency of a string changeswith the amount of tension applied to that string. A tensed string is nothing more than a spring, and allsprings have a natural frequency related to their spring constant (k) and mass (m):

f =1

2π

√

k

m

Explain how the formula for the resonant frequency of a spring/mass system (shown above) is verysimilar to the resonant frequency of an LC electrical circuit, and use the spring/mass formula to explain whya stringed instrument changes pitch when string tension changes.

This principle of mechanical resonance may be applied to the measurement of tension, which in turnmay be applied to the measurement of fluid pressure. Some years ago, the Foxboro corporation introduceda pressure transmitter using a “resonant wire” as the sensing element, and more recently the Yokogawacorporation introduced its “DpHarp” series of pressure transmitters using micro-miniature silicon resonatorsto sense pressure. Research either one or both of these pressure transmitter technologies and explain howthe principle works.

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57

Question 77

A race car team wants to be able to measure tire pressures very quickly during pit stops. Absoluteaccuracy is not as important as relative accuracy (being able to tell whether one or more tires is moreinflated than the others). They commission you to devise a very simple way to do this that does not requireletting any air out of the tire. This restriction automatically prevents you from using any sort of pneumaticpressure gauge.

Explain your solution, and also devise a way to obtain maximum accuracy with your measurement.Bonus points for devising a method that uses crude tools (easily found in a mechanic’s tool chest).

file i03589

Question 78

Question 79

Question 80

Question 81

Complete the following table of equivalent pressures. Show enough of your work that it is clear how youperformed each type of conversion (e.g. from PSIG to PSIA, from Torr to PSIA, etc.):

PSIG PSIA Torr inches W.C. (G)15

2.1900

1005

-3010

85

file i00020

58

Question 82

Suppose someone replaces the oil inside a deadweight tester with a different oil of less density than theoriginal oil. Will this alteration of oil density increase the deadweight tester’s pressure, decrease it, or notaffect the generated pressure at all? Explain your reasoning.

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00021

59

Question 83

Describe in your own words how you could build a simple U-tube manometer and use it as a pressure-measuring instrument. Furthermore, explain how you would interpret the pressure measurement from thishome-made instrument, and convert it into units of PSI (pounds per square inch).

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00019

60

Question 84

Briefly describe each of the following pressure-sensing element types, and how they work, in your ownwords:

• C-type bourdon tube

• Spiral bourdon tube

• Helical bourdon tube

• Diaphragm

• Bellows

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00022

61

Question 85

An ingenious circuit used to generate an electrical voltage signal from a differential capacitance sensoris the Twin-T diode circuit, shown here connected to a Rosemount-style differential capacitance pressuresensor:

Vout

R

R

Rload

D

D

Sensingdiaphragm

Isolatingdiaphragmdiaphragm

Isolating

Siliconefill fluid

Pressure Pressure

Solid metal

One capacitor is charged positive with respect to ground, while the other is charged negative withrespect to ground, as the AC voltage source alternates positive and negative. While one capacitor of thepressure sensor is charging, the other is discharging through Rload, producing an output voltage (Vout).

If both capacitances are equal, the output voltage will alternate equally between positive and negativevalues, having a DC average value of zero. If one capacitance is larger than the other, it will store additionalcharge on its plates, causing it to sway the output voltage of the Twin-T circuit in the direction of itspolarity. Thus, Vout becomes more positive as pressure increases on one side of the sensor, and morenegative as pressure increases on the other side of the sensor.

Based on this explanation of the Twin-T circuit’s operation, determine which side of the pictureddifferential capacitance sensor is the “High” pressure side, and which is the “Low” pressure side.

This is a graded question: you will be graded on accuracy and originality (no plagiarized answers!).file i00023

62

Question 86

A very useful principle in physics is the Ideal Gas Law, so called because it relates pressure, volume,molecular quantity, and temperature of an ideal gas together in a concise mathematical expression:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Manipulate this equation to solve for volume (V ), and again to solve for temperature (T ). Be sure toshow all your work!

V =

T =

file i03229

63

Question 87

Complete the table of values for this circuit. Be sure to show all your work!

V

I

R

P

R2

R3

R1 R2 R3 Total

12 volts

R1

220 Ω

130 Ω

470 Ω

220 Ω 130 Ω 470 Ω

file i03145

64

Question 88

Identify what will happen to the output waveform from this amplifier circuit if resistor R1 fails open,and explain why it will happen:

−

+VoutU1

Vin

R1 R2

failsopen

file i03191

65

Question 89

Calculate the power supply’s output (total) current. Be sure to show all your work!

A B

C D

3k3

4k7 2k7

1k5

+ -

Powersupply

COMA

V

V A

AOFF

Now, calculate the total current again assuming the same power supply voltage as before, but with the4700 Ω resistor failed open.

file i03151

66

Question 90

The following lamp circuit has a problem. The lamp refuses to turn on, no matter what position theswitch is set in:

+-

Battery

Switch

Lamp

Terminal block

1

2

3

4

With the switch in the on position, you measure normal battery voltage between terminals 1 and 4 onthe terminal block. Based on this information, identify which of these proposed faults could possibly accountfor the observed behavior of this circuit and which could not. Consider each fault one at a time (in otherwords, ask yourself whether or not each proposed fault – by itself – could account for the behavior of thecircuit):

• Switch failed open (contacts dirty or corroded) – possible or not possible?• Switch failed shorted (contacts welded together) – possible or not possible?• Broken wire between terminal block and battery – possible or not possible?• Broken wire between terminal block and lamp – possible or not possible?

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67

Question 91

Lab Exercise

Your team’s task is to set up a pressure measurement loop using an electronic ∆P or gauge pressuretransmitter. Instrument air pressure, either regulated or unregulated, is the suggested process variable tomeasure. Other pressure variables are open for consideration, though. Each instrument in the loop should belabeled with a proper tag name (e.g. “PT-15” for a pressure transmitter), with all instruments in each loopsharing the same loop number. Write on pieces of masking tape to make simple labels for all the instrumentsand signal lines.

Part of this lab exercise is demonstrating how to use a deadweight tester as a primary pressure source.You must either use a deadweight tester to calibrate your transmitter, or use it to test the calibration of someother pressure-measuring instrument (such as a gauge). You must also attach either a 3-valve or a 5-valvemanifold to your transmitter and demonstrate its proper use in isolating the transmitter from a process fordiagnostic or calibration purposes.

Each team must calibrate the transmitter (“trim” both the sensor and the output) to ensure itinterprets pressure accurately and outputs an accurate current. Then, each team member must configurethe transmitter for a unique range (set the LRV and URV parameters) and scale the indicator (or indicatingcontroller) to register in the proper engineering units (e.g. a pressure transmitter ranged for 30 to 70 PSIshould actually register 30 to 70 PSI back at the control room display). The accuracy of this ranging willbe checked by the instructor by applying random air pressures to the transmitter while each student verifiesthe indicator display.

Each student must diagnose a fault in the system within a 5-minute time limit, correctly identifying boththe general location and nature of the fault, and logically justifying all diagnostic steps taken. Additionaltime will be given to precisely locate and rectify the fault following successful diagnosis within the allottedtime. Failure to identify both the general location and nature of the fault within the allotted time, and/orfailing to demonstrate rational diagnostic procedure will disqualify the effort, in which case the student mustre-try with a different fault. Multiple re-tries are permitted with no reduction in grade.

Objective completion table:

Performance objective Grading 1 2 3 4 TeamComponent selection and testing mastery – – – –

Loop diagram and inspection mastery – – – –Digital trim (sensor and output) mastery – – – –Loop calibration (± 1% of span) mastery – – – –

Deadweight tester usage mastery – – – –Transmitter valve manifold usage mastery – – – –Troubleshooting (5 minute limit) mastery – – – –

Lab question: Diagnosis proportional – – – –Lab question: Instruments proportional – – – –

Lab question: Math proportional – – – –Lab question: Tools/safety proportional – – – –

Lab questions (reviewed between instructor and student team in a private session)

• Diagnosis• Explain what will happen (and why) if the 250 ohm resistor fails open in the transmitter circuit• Explain what will happen (and why) if the 250 ohm resistor fails shorted in the transmitter circuit• Explain what will happen (and why) if the transmitter cable fails open• Explain what will happen (and why) if the transmitter cable fails shorted• Explain what will happen (and why) if loop power supply voltage is too low

68

• Identify what things may be determined about a malfunctioning measurement loop from a singlemeasurement of the 4-20 mA process variable signal (e.g. suppose the indicator fails to accuratelyregister the pressure applied to a transmitter – how could a loop current measurement help you in yourdiagnosis?)

• Instruments• Explain how a tube fitting seals against fluid leaks• Explain how a tapered-thread pipe fitting seals against fluid leaks• Identify the “high” and “low” pressure ports on your pressure transmitter, and explain their significance• Identify and explain range turndown on your transmitter (also called rangedown)• Identify and explain the purpose of damping on your transmitter• Explain how a 4-20 mA current signal conveys information• Explain the operating principle of the pressure transmitter (as detailed as possible)• Identify and explain zero and span adjustments on your transmitter• Explain how to use a ∆P gauge or transmitter to measure positive pressure versus measuring a vacuum• Identify the purpose of a fill fluid inside the pressure transmitter capsule• Identify proper fill fluid types for pressure instruments going in to different processes (pure oxygen, food

processing, medical, etc.)• Explain proper three-valve manifold operating procedures (for both placing in and taking out of service)• Identify and explain maximum working pressure of your pressure transmitter

• Math (no calculator allowed!)• Calculate the correct loop current value (mA) given a pressure transmitter calibration range and an

applied pressure• Calculate the pressure applied to a transmitter given a calibration range and the measured loop current

value• Calculate the percentage of span error for a transmitter given a calibration range and an As-Found

calibration table• Calculate the allowable pressure error for a transmitter given an allowable percentage of span error and

a calibration range• Convert between different pressure units, without relying on the use of a reference for conversion factors

(i.e. you must commit the major conversion factors to memory)

• Tools/Safety• Demonstrate how to properly use a deadweight tester as a standard pressure source• Explain why a deadweight tester works as a standard pressure source• Demonstrate how to shut off and tag out electrical power to your loop instruments• Identify where the danger tags are kept (for tagging out devices)• Identify and explain low- and high-pressure pistons for deadweight tester• Identify and explain the effect of entrapped air in a deadweight tester• Demonstrate how to properly use an air pump as pressure source• Explain importance of deadweight tester fluids when calibrating pressure instruments for different

processes (pure oxygen, food processing, medical, etc.)

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69

Question

92

Loop

dia

gra

mte

mpla

te

Description Manufacturer Model Notes

Loop Diagram: Revised by: Date:

Tag # Input range Output range

70

Loop diagram requirements

• Instrument “bubbles”• Proper symbols and designations used for all instruments.• All instrument “bubbles” properly labeled (letter codes and loop numbers).• All instrument “bubbles” marked with the proper lines (solid line, dashed line, single line, double lines,

no lines).• Optional: Calibration ranges and action arrows written next to each bubble.

• Text descriptions• Each instrument documented below (tag number, description, etc.).• Calibration (input and output ranges) given for each instrument, as applicable.

• Connection points• All terminals and tube junctions properly labeled.• All terminal blocks properly labeled.• All junction (“field”) boxes shown as distinct sections of the loop diagram, and properly labeled.• All control panels shown as distinct sections of the loop diagram, and properly labeled.• All wire colors shown next to each terminal.• All terminals on instruments labeled as they appear on the instrument (so that anyone reading the

diagram will know which instrument terminal each wire goes to).

• Cables and tubes• Single-pair cables or pneumatic tubes going to individual instruments should be labeled with the field

instrument tag number (e.g. “TT-8” or “TY-12”)• Multi-pair cables or pneumatic tube bundles going between junction boxes and/or panels need to have

unique numbers (e.g. “Cable 10”) as well as numbers for each pair (e.g. “Pair 1,” “Pair 2,” etc.).

• Energy sources• All power source intensities labeled (e.g. “24 VDC,” “120 VAC,” “20 PSI”)• All shutoff points labeled (e.g. “Breaker #5,” “Valve #7”)

71

Sam

ple

Loop

Dia

gra

m(u

sing

asin

gle

-loop

contro

ller)

Process areaField panel Control room panel

Controller

Resistor

I/P transducer

Control valve

I/P

ES 120 VAC

AS 20 PSI

Loop Diagram: Furnace temperature control

TT205

JB-12

TB-15

TB-15

3

4

1

2

Temperature transmitterTT-205 Rosemount 444

TE205

CP-1

TB-11

TB-11

1

2

7

Vishay 250 ΩTY-205a

TIC-205 Siemens PAC 353

TY-205b

TV-205 Fisher Easy-E 3-15 PSI

Fisher

H

N

3

4

22

21

19

18

TY205b

TY

205a

Breaker #4Panel L2

5

6Cable TY-205b

Cable TT-205 Cable TT-205

Cable TY-205b

TIC205

Revised by: Mason Neilan

TV205

Tube TV-205

Column #8Valve #15

546

0-1500oF 0-1500oF

Fail-closed

Reverse-acting control

TE-205 Thermocouple Omega Type K Ungrounded tip

Red

BlkRed

Yel Red

Blk

Red

Blk

Red

Blk

Wht/Blu

Blu Blu

Wht/Blu

Cable 3, Pr 1

Cable 3, Pr 2

Wht/Org

Org Org

Wht/Org

Blk

Red

Blk

Red

Blk

Wht

Red

Blk

Red

Blk

Upscale burnout

Description Manufacturer Model Notes

Date:

Tag # Input range Output range

0-1500o F 4-20 mA

4-20 mA 3-15 PSI

0-100%

1-5 V 0-1500o F

April 1, 2007

72

Sam

ple

Loop

Dia

gra

m(u

sing

DC

Scontro

ller)

Field process area

Description Manufacturer Model Notes

Loop Diagram: Revised by: Date:

DCS cabinet

Red

Blk

Red

Blk

Red

Blk

Fisher

Fisher

Tag # Input range Output range

Blue team pressure loop April 1, 2009

Card 4

Card 6Channel 6

Channel 611

12

29

30

Red

Blk

TB-80

TB-80

Field panel JB-25

TB-52

TB-52

PT-6 Pressure transmitter Rosemount 3051CD 0-50 PSI 4-20 mA

PIC6

PT6

Cable 4, Pr 1

Cable 4, Pr 8

1

2

15

16

Cable PT-6

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Cable PV-6

11

12

11

12PY6

AS 20 PSI

PV6

0-50 PSI

I/P

0-50 PSI

846

Emerson DeltaV 4-20 mA 4-20 mA HART-enabled inputPIC-6

PY-6

PV-6

I/P transducer

Controller

Control valve Vee-ball

4-20 mA 3-15 PSI

3-15 PSI 0-100% Fail-open

Duncan D.V.

Tube PV-6

Cable PT-6

Cable PV-6

Analog input

Analogoutput

Direct-acting control

H

L

73

Sam

ple

Loop

Dia

gra

m(u

sing

pneum

atic

contro

ller)

Description Manufacturer Model Notes

Loop Diagram: Revised by: Date:

Tag # Input range Output range

LT24

In

H

LOut

C

D

A.S. 21 PSI

Tube LT-24a Tube LT-24b

A.S. 21 PSI

Process areaBulkhead panel

14

B-104Control panel CP-11

Tube LV-24

LV24

Tube LV-24

Supply

LIC

24

Tube LV-24

(vent)

Sludge tank level control I. Leaky April 1, 2008

LT-24 Level transmitter Foxboro 13A 25-150 "H2O 3-15 PSI

3-15 PSI 3-15 PSIFoxboroLIC-24 130

LV-24 Fisher Easy-E / 667 3-15 PSI 0-100% Fail closedControl valve

Controller

file

i00654

74

Question 93

Connect an “ice-cube” relay to a DC voltage source and a switch such that the relay will energize whenthe switch is closed. All electrical connections must be made using a terminal strip (no twisted wires, crimpsplices, wire nuts, spring clips, or “alligator” clips permitted).

This exercise tests your ability to properly interpret the “pinout” of an electromechanical relay, properlywire a switch to control a relay’s coil, and use a terminal strip to organize all electrical connections.

Terminal strip SwitchRelayRelay socket

The following components and materials will be available to you during the exam: assorted “ice cube”relays with DC-rated coils and matching sockets ; assorted switches ; terminal strips ; lengths ofhook-up wire ; battery clips (holders).

You will be expected to supply your own screwdrivers and multimeter for assembling and testing thecircuit at your desk. The instructor will supply the battery(ies) to power your circuit when you are readyto see if it works. Until that time, your circuit will remain unpowered.

Study reference: the “Control Relays” section of Lessons In Industrial Instrumentation.file i03772

75

Answers

Answer 1

I’ll let you figure this out on your own!

Answer 2

Answer 3

Answer 4

Force at large piston = 100 pounds. I’ll let you calculate the fluid pressure on your own, as well asexplain the relationship of Pascal’s Principle to this system.

Answer 5

Ideally, the secondary piston’s position will have no effect on the oil pressure sent to the gauge.Consequently, the gauge indication should not change.

Answer 6

Answer 7

Answer 8

• 25 PSI = 172.37 kPa

• 40 ”W.C. = 1.4451 PSI

• 5.60 bar (gauge) = 81.221 PSI

• 3 atm = 44.088 PSIA

• 1,200 ”Hg = 16,314.51 ”W.C.

• 12 feet W.C. = 5.2022 PSI

• 4 PSI vacuum = 10.7 PSIA

• 110 kPa = 441.622 ”W.C.

• 982 mm Hg = 38.661 ”Hg

• 50 Pa = 0.007252 PSI

• 21 atm = 628.522 ”Hg absolute

• 270 PSIG = 19.367 atm

Answer 9

Partial answer:

• P = 1100 PSI F = 21,598.4 lbs

• P = 461 kPa F = 1312.8 lbs

• P = 2.77 bar F = 788.8 lbs

Answer 10

76

Answer 11

I’ll answer this question with an equation:

P =F

A

Where,P = PressureF = ForceA = Area

Answer 12

The fluid pressure will exert an outward force on the cylinder walls, like this:

Force

pres

sure

77

Answer 13

A pushing force on the rod will compress the rubber ball to a smaller diameter. A pulling force willexpand it to a larger diameter.

Rubber ball Rubber ballcompresses expands

Answer 14

Absolute pressure is the measurement of a pressure as compared to a pure vacuum. Atmospheric(“barometric”) pressure, like the pressure figures reported by meteorologists, is an example of absolutepressure measurement.

Gauge pressure is the measurement of a pressure as compared to the pressure of Earth’s atmosphere.The pressure indicated by a pressure gauge (like an oil pressure gauge for a car engine, or a tire pressuregauge) is an example of gauge pressure. When vented, such a gauge will register zero, even though there isstill absolute pressure all around us due to Earth’s atmosphere.

Differential pressure is the measurement of a difference between two different pressures. In essence, allpressure measurements are differential in nature: notice how absolute and gauge pressures are defined interms of a comparison of one pressure against another!

Suffixes are sometimes appended to pressure units to distinguish between absolute (A), gauge (G), anddifferential (D) pressures. For example, you might see an absolute pressure represented as “150 PSIA”, agauge pressure as “35 PSIG”, or a differential pressure as “86.5 PSID”. If no such suffix is given, the pressureunit is assumed to be gauge.

Some units of pressure measurement are always absolute, never gauge or differential. These units includethe atmosphere (14.7 PSIA), the bar (very close to 1 atmosphere – think of it as a “metric” atmosphere),and the torr, which is absolute millimeters of mercury column.

Answer 15

Absolute pressure = 2,014.7 PSIA. Gauge pressure = 2,000 PSIG. Differential pressure (between tankand water) = 1,978 PSID.

78

Answer 16

406.91 inches, which is a little bit less than 34 feet.

Deeper wells may be tapped by using submersible pumps (pumps located inside the well, near thebottom):

Pump

Follow-up question: demonstrate how we could have arrived at an approximate answer by using roundedfigures for our unit-conversion constants, and “mental math” instead of a calculator.

Answer 17

With no nozzle on the end of the hose, the end may be raised a maximum of 184.54 feet. With a nozzlein place, the hose end may be raised only 115.34 feet.

Follow-up question #1: explain how this problem relates to safety and firefighting.

Follow-up question #2: demonstrate how we could have arrived at an approximate answer by usingrounded figures for our unit-conversion constants, and “mental math” instead of a calculator.

Answer 18

Scenario #1: Force on each wall = 48 pounds

Scenario #2: Force generated by piston = 4,712.39 pounds

Scenario #3: Force generated by piston = 136.19 pounds

Follow-up question: demonstrate how we could have arrived at approximate answers by using roundedfigures for our unit-conversion constants, and “mental math” instead of a calculator.

79

Answer 19

PSIG PSIA inches Hg (G) inches W.C. (G)18 32.7 36.65 498.25

385.3 400 784.5 1066516.21 30.91 33 448.62.168 16.87 4.413 60222.0 236.7 452 6145.10.4335 15.13 0.8826 12-13.7 1 -27.89 -379.2-5 9.7 -10.18 -138.4

Answer 20

Answer 21

Answer 22

Answer 23

Answer 24

Answer 25

Applied pressure = 1.193 kPa

Answer 26

• 25 PSIA = 1.701 atm

• 340 ”W.C. = 26.983 PSIA

• 0.73 bar (gauge) = 21.557 ”Hg

• 5.5 atm = 4,180 torr

• 2,300 cm Hg = 12,717.72 ”W.C.A

• 500 m torr = 0.0096683 PSIA

• 91.2 cm W.C. = 8.9434 kPa

• 110 kPa = 441.62 ”W.C.

• 620 mm HgA = 620 torr (A “trick” question . . .)

• 77 Pa = 14.711168 PSIA

• 1 atm = 406.91 ”W.C.A

• 270 PSIA = 18.367 atm

80

Answer 27

• 5 PSI vacuum = 9.7 PSIA

• 25 ”Hg vacuum = 2.421 PSIA

• 2,800 µ torr = 0.3733 PaA

• -59 ”W.C. = 649.98 torr

• 4,630 PaA = -14.028 PSI

• 0.05 atm = -386.56 ”W.C.

• -3 kPa = 0.9704 atm

• 10 feet W.C. vacuum = 21.103 ”HgA

• 300 cm Hg = 4.946 atm

• -2 mm W.C. = 1.0133 bar (absolute)

• 4 atm = 1,627.63 ”W.C.A

Answer 28

Answer 29

Answer 30

Answer 31

This is perfectly legitimate, because in either case all the pressure units involved in each conversion areof the same type: either all gauge or all absolute. Where we encounter difficulties is if we try to mix differentunits in the same “unity fraction” conversion that do not share a common zero point.

A classic example of this mistake is trying to do a temperature conversion from degrees F to degrees Cusing unity fractions (e.g. 100o C = 212o F):

(

60o F

1

) (

100o C

212o F

)

6= 28.3o C

This cannot work because the technique of unity fractions is based on proportion, and there is no simpleproportional relationship between degrees F and degrees C; rather, there is an offset of 32 degrees betweenthe two temperature scales. The only way to properly manage this offset in the calculation is to include anappropriate addition or subtraction (as needed).

However, if there is no offset between the units involved in a conversion problem, there is no need toadd or subtract anything, and we may perform the entire conversion using nothing but multiplication anddivision (unity fractions). Such is the case if we convert pressure units that are all gauge, or if we convertpressure units that are all absolute.

To summarize, it is perfectly acceptable to construct a unity fraction of 27.68 ”W.C.2.036 ”Hg

because 0 ”W.C.

is the same as 0 ”Hg (i.e. they share the same zero point; there is no offset between units ”W.C. and ”Hg).

Likewise, it is perfectly acceptable to construct a unity fraction of 27.68 ”W.C.A2.036 ”HgA

because 0 ”W.C.A is the

same as 0 ”HgA (i.e. they share the same zero point; there is no offset between units ”W.C.A and ”HgA).

Answer 32

Applied pressure = 2.5 ”W.C.

81

Answer 33

1 inch of bubble motion represents 0.02 inches of water column pressure (differential), or 2/100 ”W.C.,applied across this micromanometer.

Answer 34

The manometer will register falsely high, showing greater differential pressure than what is actuallythere. If you are having difficulty figuring this out, imagine if the liquid moving through the pipe was justas dense as the mercury within the manometer: what would that do to the mercury in the manometer givenany applied ∆P? In other words, set up a thought experiment with absurdly (simple) conditions and thenlook for patterns or trends which you may generalize for any condition.

Challenge question: derive a mathematical correction factor for interpreting the manometer’s indicationto yield true inches of mercury ∆P.

Answer 35

k = 134.4

Answer 36

P

V

Note that the function is a curve and not a straight line! In essence, the function plotted is this:

P =k

V

Where k is a constant equal to nRT .

Answer 37

Answer 38

Answer 39

Answer 40

Answer 41

Answer 42

Answer 43

82

Answer 44

Answer 45

Answer 46

Answer 47

Answer 48

Answer 49

The parts in this gauge mechanism would move as such:

Appliedpressure

Pointer

Pressure gauge

Bourdontube

mechanism

Possible things to change to make this pressure-measuring mechanism more sensitive:

• Decrease the spring rate (“stiffness”) of the bourdon tube• Shorted the arm of the sector gear (the portion to the right of the pivot, joining with the link)• Increase the sector gear radius• Decrease the pinion gear radius

83

Answer 50

Here is one example of how a pressure gauge might respond in a non-linear fashion to the same fiveapplied pressures, while still being accurate at the LRV and URV points:

0 500

250

125 375

0 500

250

125 375

0 500

250

125 375

0 PSI applied 125 PSI applied 250 PSI applied

0 500

250

125 375

0 500

250

125 375

375 PSI applied 500 PSI applied

actual

(desired)

actual (desired)

actual

(desired)

Here, the gauge reads high at the 25% point (125 PSI), slightly low at the 50% point (250 PSI), andlow at the 75% point (375 PSI), while still accurate at 0% (0 PSI) and 100% (500 PSI).

Any adjustment that affects the traveling angle of the mechanism will have an effect on linearity. Some(high-quality) pressure gauge mechanisms are equipped with an adjustable-length link to facilitate changesto this angle:

Appliedpressure

Pointer

Link

Bourdontube

(adjustable length)

Travelingangle

It is sage advice to leave all angle adjustment(s) untouched until all possible zero and span adjustmentshave been made to the instrument. Usually, it is possible to get a nonlinear instrument to read withinspecified tolerance in a 5-point calibration just by adjusting the zero and span adjustments.

84

In many mechanical instruments, a simple linearity alignment is to apply a 50% input signal and checkfor link/lever perpendicularity (that all links and levers intersect at 90o angles to each other).

Answer 51

(1) The accuracy of a deadweight tester is fixed by three fundamental variables, all of which arequite constant, two of which can be manufactured to highly accurate specifications, and the thirdbeing a constant of nature:

• The mass of the calibration weights• The area of the primary piston• The gravity of the Earth

(2) If a deadweight is not level, the force generated by the precision weights will not be parallel tothe primary piston’s axis of travel, meaning that the piston will not support their full weight.

(3) Entrapped air will make the piston’s motion “springy” rather than solid and secure.

(4) Spinning the primary piston eliminates static friction, leaving only dynamic friction (which ismuch less) to interfere with gravity’s force on the primary piston.

Answer 52

The accuracy of a manometer is fixed by two fundamental variables, both of which are quite constant:

• The density (mass per unit volume) of the manometer liquid• The gravity of Earth

So long as these two variables do not change, neither will the accuracy of the manometer.

Answer 53

Net piston force = 890.936 pounds.

Answer 54

Net force = 4,319.69 pounds, in the downward direction.

Answer 55

Actuating the hand pump introduces more air molecules to the system (n). Assuming temperature (T )remains constant, the air pressure (P ) will increase in inverse proportion to the volume (V ) of the pressurevessel for each additional stroke of the pump.

Follow-up question: If we wished the pressure to increase less for every stroke of the pump, would wewant a smaller pressure vessel or a larger pressure vessel? Explain your answer.

Challenge question: suppose a technician follows these steps in using this system.

• Close valve 2, open valves 1 and 3• Pump several strokes’ worth of air into the pressure vessel• Close valves 1 and 3• Slowly open valve 2 until manometer registers desired pressure, then close

Is the air pressure going to the instrument under test greater than, less than, or equal to the air pressurein the vessel?

85

Answer 56

To instrumentunder test

Low-rangevoltmeter+

−High voltage

source

3-terminalIC regulator

I’ll leave the explanation to you!

Follow-up question #1: explain what you could do with one or both of the two needle valves to increasethe amount of pressure sent to the instrument under test.

Follow-up question #2: explain why placing a valve in “series” with the regulator’s output will notadjust pressure to the instrument under test or the manometer.

Air compressor

Manometer

Receiver

To instrumentunder test

Pressureregulator

This valve will notadjust pressure!

Answer 57

I’ll let you figure this out on your own.

Answer 58

It is an “anti-backlash” spring, supplying enough torque to rid the sector/pinion gear set of any “slack”or “play,” so that the pointer always responds to the slightest change in bourdon tube position.

86

Answer 59

Multiple-turn bourdon tubes generate more motion than C-shaped tubes, for the same rated pressures.Therefore, they do not require gears for multiplication of motion to move a pointer. By eliminating gearsin the design, the instrument will have better (decreased) hysteresis and deadband, and be more tolerant ofvibration.

Answer 60

Answer 61

First transmitter design:Input range: 0 to 15 PSIOutput range: 0 to 10 volts DC

Last transmitter design:Input range: 0 to 15 PSIOutput range: 1 to 5 volts DC

Follow-up question: show the current in both circuits using both conventional flow notation and electronflow notation.

Answer 62

Answer 63

Answer 64

Answer 65

Answer 66

Answer 67

Answer 68

Partial answer:

• Resistor R1 failed open Possible• Resistor R1 failed shorted• Resistor R2 failed open• Resistor R2 failed shorted Possible• Strain gauge (measurement) failed open• Strain gauge (measurement) failed shorted• “Dummy” gauge (temperature compensation) failed open• “Dummy” gauge (temperature compensation) failed shorted Not possible• Voltage source is dead (no voltage output at all)

87

Answer 69

• 22 PSIG = 36.7 PSIA

• 13 kPa = 52.19 ”W.C.

• 81 kPa = 11.75 PSI

• 5 atm = 73.5 PSIA

• 200 ”Hg = 2719 ”W.C.

• 17 feet W.C. = 15.01 ”Hg

• 8 PSI vacuum = 6.7 PSIA

• 900 Torr = 481.9 ”W.C.A

• 300 mm Hg = 5.801 PSI

• 250 ”W.C. = 0.6227 bar (gauge)

• 70 ”W.C. = 5.149 ”Hg

• 300 PSIG = 21.41 atm

Answer 70

Atm PSIG inches W.C. (G) PSIA3.5 36.75 1017.3 51.456.51 81 2242 95.722.71 319.1 8834 333.8

0 -14.7 -406.9 01.017 0.2572 7.12 14.9625.03 353.3 9779.6 3681.136 2 55.36 16.7100 1455.3 40284 1470

Answer 71

I’ll let you figure out the answers to this question on your own!

Answer 72

Note very carefully how the two secondary coils are connected in series-opposing (as denoted by thephase dots)! This detail is essential in figuring out how the LVDT works.

Follow-up question: LVDT position sensors have many favorable characteristics when compared topotentiometers. Identify some of these advantages, and explain why they would be relevant to this pressure-measurement application.

Answer 73

Hint: although it may not look like it at first, the two resistors form a bridge circuit with the differentialcapacitor.

Answer 74

There is a lot of literature available discussing differential capacitance capsule technology, so I will referyou to that!

88

Answer 75

The output voltage will be positive with respect to ground if C > C ′ and negative if C ′ > C.

Answer 76

Hint: you may find that Yokogawa’s DpHarp product is easier to obtain information on, being a morerecent product.

Answer 77

Did you really think I would reveal possible solutions to the problem this easily?

Answer 78

Answer 79

Answer 80

Answer 81

This is a graded question – no answers or hints given!

Answer 82

This is a graded question – no answers or hints given!

Answer 83

This is a graded question – no answers or hints given!

Answer 84

This is a graded question – no answers or hints given!

Answer 85

This is a graded question – no answers or hints given!

Answer 86

This is a graded question – no answers or hints given!

Answer 87

This is a graded question – no answers or hints given!

Answer 88

This is a graded question – no answers or hints given!

Answer 89

This is a graded question – no answers or hints given!

Answer 90

This is a graded question – no answers or hints given!

Answer 91

89

Answer 92

Your loop diagram will be validated when the instructor inspects the loop with you and the rest of yourteam.

Answer 93

90