BULLETIN TS-102(N)

TEMPERATURE SENSORS & INSTRUMENTS

Sections included in this file are indicated below:

�A Introduction

B Temperature Sensor& Transmitter Assemblies

C RTD &Thermocouple Probes

D Accessories

E Temperature Instruments

F Sanitary Sensors

G MiniatureBearing Detectors

H Stator Winding Detectors

I HVAC/R Sensors

J Thermal-Ribbons™

K Ceramic Elements

L PrecisionReference Thermometers

Minco: Your Source For SensorsMinco has designed and manufacturedRTD’s for more than 45 years. We havethe capabilities and experience to puttogether a proven sensing solution, at acost-effective price, for your application.

The right sensorNo sensor manufacturer offers morestyles and variations. From miniaturedetectors to 50 foot averaging thermo-meters, from flexible Thermal-Ribbons toheavy duty probe assemblies, ourselection lets you choose the best modelfor your needs. We can supply platinum,nickel, nickel-iron, and copper RTD’swith curves to match any instrument-tation. And Minco also offers thermo-couples and thermistors mechanicallyinterchangeable with RTD models tohelp you standardize installations.

Single source manufacturingMinco builds sensors from start to finish.We manufacture our own sensingelements, machine our own cases andfittings, and assemble finished parts. Thatgives us complete control over productquality, plus flexibility in adaptingdesigns to customer requirements.

Custom designStock solutions aren’t always the bestsolutions. Minco has designed over 7000custom sensors, each with uniquefeatures for better performance at alower price. Let our engineers suggestinnovative ideas to tailor a sensor to yourapplication.

Quality above allMinco sensors have proven theirreliability in the most critical arenas. TheSpace Shuttle uses our RTD’s. So donuclear plant safety systems, rocketmotors, power generators, missiles, andcalibration labs. Quality comes first atMinco. Documented and auditedprocedures, continuous qualityimprovement goals, and employeeinvolvement programs set a highstandard throughout the company.

Credit cardsMinco accepts MasterCard, Visa, andAmerican Express.

Extensive stock for urgentneedsWhen you need it right now, this is theright place. Minco stocks more than 250different types of sensors. Cut-to-lengthprobes are one example. We can take aprobe from the shelf, trim it to theproper size, add fittings, connectionhead, transmitter, and thermowell, andship it to you overnight. Look for thissymbol:

IN STOCK

About Minco

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Application ideas............................A-4–5Custom design ...............................A-6–7Selection guide...............................A-8–9Sensor comparison..........................A-10RTD elements and tolerance .......... A-11Thermocouple limits of error............A-11Industry specifications, TCR ............A-122-wire, 3-wire, 4-wire circuits............A-13Resistance, millivolt tables .........A-14–15Map...................................................A-16

Introduction Temperature Sensor &Transmitter Assemblies

RTD and ThermocoupleProbes

Accessories TemperatureInstruments

Sanitary Sensors

Miniature BearingDetectors

Stator WindingDetectors

HVAC\R Sensors

Thermal-Ribbons™ Ceramic Elements Precision ReferenceThermometers

Related literature: L-7 Product and subject indexes: Inside rear cover

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Typical Applications

Restaurant fryerA fast response RTD monitors oiltemperature for perfect cooking re-sults.

Medical freezerRTD’s monitor temperatures as lowas -120°C in freezers used to storetissues and organs. Close control andsensor reliability are essential.

Humidity calibrationA wet bulb/dry bulb humidity stan-dard contains two gold-plated preci-sion platinum thermometers.

Inertial guidance systemThis flexible Thermal-Ribbon helpsto control gyro temperatures in iner-tial guidance systems.

Hydraulic systemsInstalled in hydraulic lines, this RTDmonitors oil temperatures to preventoverheating.

Military vehiclesThis RTD contains an integralWheatstone bridge. It monitors en-gine temperatures for computerizeddiagnostics.

Industrial/Commercial Machinery

Aerospace/Defense

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Process Control and Energy Management

Centrifugal compressorThis assembly includes an RTDprobe, thermowell, and 2-wireTemptran™ transmitter. It monitorsthe air outlet stream.

Room air sensingMinco’s sensor/transmitter is spe-cially designed to reduce self-heatingeffects for accurate readings.

Pipe surface measurementA flexible Thermal-Ribbon, taped toa pipe surface, eliminates the needfor thermowell installation.

Motor/Machinery Protection

BearingsMiniature detectors fit beneath thebabbitt surface of bearing shoes toprovide early warning of failure.

Stator windingsFlat “stick” RTD’s track winding tem-peratures to prevent motor burnout.

Temperature alarmMinco’s programmable monitortracks up to eight sensing points andautomatically activates relays and anaudible alarm.

Page A-6 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102

Custom Design

Custom Design For Better Performance

This bulletin contains a wide array ofsensor styles to fit most applications.But if you have special require-ments—or will purchase sensors inquantity for an OEM design—a cus-tom sensor can improve accuracyand reduce cost at the same time.And no one offers more custom de-sign possibilities than Minco.

Elements to match anycurveWe can supply sensors to work withnearly any type of instrument input:� Platinum RTD’s with TCR’s from

0.00375 to 0.003927� Nickel, copper, and nickel-iron

RTD elements� Non-standard curves� Base resistances up to thousands

of ohms� Thermistors or thermocouples� Linearizing transmitters with 4 to

20 mA, 1 to 5 VDC, or other volt-age/current outputs

Machining and materialsA sensor’s case construction deter-mines its thermal response and resis-tance to corrosive media. Minco hasan advanced machine shop withCAD/CAM capability for economicproduction of cases and fittings.

Select from a variety of materials:� Stainless steel in various grades� Brass� Copper and beryllium copper� Monel� Hastelloy� Titanium� Rubber, PTFE, plasticsWe can plate with nickel, gold, andother metals. Additional services in-clude electropolishing, passivating,and pressure testing.

LeadwiresRTD’s, thermocouples, andthermistors may be fur-nished with many differ-ent types of leadwireand cables to meet ap-plication parameters:� PTFE, silicone rub-

ber, polyimide,mica/glass, and glassbraid insulation

� Stainless steel over-braid or flexible armor

� UL recognized wire� Integral feedthroughs� Connectors assembled to probes

or leadwires� Flat ribbon leads or

sensor/flex-circuit hybrids

LaminationMinco’s winding and laminationtechnology enables manufacture offlat, flexible sensors in any size orshape. The custom Thermal-Ribbonbelow has a wire element to averagetemperatures over its entire area.

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TestingMinco has complete in-house testingand metrology equipment to meetstringent quality requirements:� NIST traceable calibrations� Hydrostatic testing of thermowells� Helium leak testing for nuclear re-

quirements� Automated resistance measure-

ment� Humidity testing

Critical point calibrationHere’s a simple idea to improve ac-curacy with little additional cost.Suppose you want RTD’s inter-changeable within 0.5°C at a criticalcontrol point of 200°C. Theinterchangeability for a typical RTD(IEC 751, Class B) is ±0.3°C at 0°C,±1.3°C at 200°C. The tolerance bandlooks like this:

You could specify a tighter overallcalibration in order to get the desiredtolerance at 200°C. But that wouldincrease sensor cost. Instead, Mincocan calibrate the sensor to have itsnarrowest tolerance at the criticaltemperature:

You now have a sensor with ±0.3°Ctolerance at 200°C. And the cost isno more than a standard sensor involume.

Sensor/instrument systemsMinco manufactures transmitters,readouts, controllers, and alarms inaddition to sensors. Ordering sensorsand instruments in sets offers manybenefits:� Transmitters can be calibrated to

individual sensors rather than

nominal curves. That way, overallaccuracy is not dependent on sen-sor tolerance.

� There are no worries about sensorand instrument compatibility.

� Entire systems can be custom de-signed with the best feature/pricepackage for the intended applica-tion.

� You can combine Thermofoil™heaters with sensors andcontrollers for ready-to-usethermal systems.

Designing for accuracyHow accurate is a temperature sen-sor? To many, the answer to thisquestion is the sensor’sinterchangeability specification. Forexample, 100 � platinum RTD’s aretypically interchangeable within 0.1� or 0.3°C at 0°C.

But interchangeability only tellshow closely the electrical characteris-tics of a sensor conform to its pub-lished tables. What you really wantto know is how much the tempera-ture seen at your readout or control-ler deviates from the actual tempera-ture of the material you are sensing.Interchangeability is only one of thepotential sources of error in the sys-tem, and it is usually not the largest.Following are some other errormodes along with suggested solu-tions.

Repeatability/stability: Repeatabil-ity tells how well the sensor repeatssubsequent readings at the sametemperature. Stability is the absenceof long term drift. In many cases, theuser is less concerned with absoluteaccuracy than with the ability of asensor to maintain a process at thesame point once properly set.Solution: Platinum RTD’s are themost stable sensor in common useand are used to interpolate over thestandard temperature scale from -260to 962°C. Ordinary industrial modelswill drift less than 0.1°C per year innormal use.

Time lag: When temperatureschange rapidly, sensors may notkeep up.Solution: Minco specializes in fastresponse RTD’s. Most models in thiscatalog have a time constant of 2seconds or less. Certain custom de-signed models are faster yet.

Time constant is defined as thetime it takes a sensor to reflect 63%of a step temperature change:

Conduction errors: Heat con-ducted into sensors from ambient airalters the temperature of the sensingtip.Solution: Use smaller sensors ortip-sensitive probes, and be surethey are sufficiently immersed or em-bedded in the sensed medium.

Point sensing errors: In placeswhere temperatures are stratified orgradients are large, the temperatureat a single point may be unrepresen-tative or misleading.Solution: Use temperature averagingprobes or Thermal-Ribbons.

Leadwire resistance: Resistance inthe leads between RTD’s and controlpoints elevates apparent readings.Solutions:� Specify sensors with higher

resistances.� Use 3 or 4-wire compensating cir-

cuits (see page A-13).� Eliminate leadwire effects with a 4

to 20 mA transmitter (Section E).

Self-heating: The measuring currentthrough an RTD can raise its temper-ature above the true value.Solution: As a general rule, limitcurrent to 5 mA for industrial appli-cations. Most Minco RTD’s, and es-pecially Thermal-Ribbons, have alarge surface area to dissipate heatand reduce self-heating effects.

+2

0°C-1

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Page A-8 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102

Sensor Selection Guide

Sensor Type DescriptionTemperature

Range*

RTD ElementThermocouple

Junction

Th

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Assemblies Probes supplied complete withfittings, connection heads,thermowells, and optionaltransmitters

-269 to 550°C

-452 to 1022°F � � � � � � �

Probes Industrial probe type sensors:tip-sensitive, fast response, andhigh temperature models

-269 to 850°C

-452 to 1562°F � � � � � � �

Sanitary RTD’s 3-A certified for clean-in-placeinstallations

-100 to 200°C

-148 to 392°F �

Bearing Detectors &Miniature RTD’s

Miniature encased sensingelements

-184 to 260°C

-300 to 500°F � � � � � � �

Stator WindingDetectors

Flat, laminated “stick” sensors 180°C (356°F)max.

� � � � � � �

HVAC Thermometers Sensors and transmittersdesigned for HVAC systems

-45.5 to 135°C

-50 to 275°F � � �

Thermal-Ribbons™ Flat, flexible sensors for surfacemounting

-200 to 200°C

-328 to 428°F � � � � � � � �

Ceramic Elements Wire-wound and thin-film elements -200 to 850°C

-328 to 1582°F �

Precision LaboratoryThermometers

Reference grade platinumthermometers

-260 to 660°C

-436 to 1220°F �

* Temperature range of individual models may vary.

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Typical ApplicationsSee

Section

Process control Bearings Air StreamsOil baths

B

General purpose sensing Stacks BearingsCommercial ovens Fryers and griddles Plastics processingScientific instruments Truck/vehicle engines Incubators

C

Food, dairy, pharmaceutical, and biotechnological processing equipment

F

Babbitted bearings General purpose sensing Gas flow metersCircuit boards

G

Motor and generator stator windings Level sensing systemsTransformer coils

H

Energy Monitoring and Control Systems (EMCS) FreezersLow cost industrial sensors Medical refrigerationAveraging sensors for storage tanks Exhaust fan control

I

Aerospace instruments Medical devices Motor windingsAircraft windshields Thermal processing equipment Pipe temperatureThermocouple cold junction compensation Environmental chambers

J

Assembly into probes High temperature sensing Miniature probesNuclear applications Air flow sensing

K

Laboratory references Cryogenic sensing AvionicsTest stands Sensor calibration

L

Page A-10 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102

RTD, Thermocouple, or Thermistor?

Resistance temperaturedetectors (RTD’s)An RTD sensing element consists ofa wire coil or deposited film of puremetal. The element’s resistance in-creases with temperature in a knownand repeatable manner. RTD’s ex-hibit excellent accuracy over a widetemperature range and represent thefastest growing segment among in-dustrial temperature sensors. Theiradvantages include:� Temperature range: Models in this

bulletin cover temperatures from-260 to 850°C (-436 to 1582°F).

� Repeatability and stability: Theplatinum resistance thermometer isthe primary interpolation instru-ment used by the National Insti-tute of Standards and Technologyfrom -260 to 962°C. Minco offerslaboratory models stable within0.0025°C per year. Even ordinaryindustrial RTD’s typically drift lessthan 0.1°C/year.

� Sensitivity: The voltage drop acrossan RTD provides a much larger out-put than a thermocouple.

� Linearity: Platinum and copperRTD’s produce a more linear re-sponse than thermocouples orthermistors. RTD non-linearitiescan be corrected through properdesign of resistive bridge net-works.

� Low system cost: RTD’s use ordi-nary copper extension leads andrequire no cold junction compen-sation.

� Standardization: Manufacturers of-fer RTD’s to industry standardcurves, most commonly 100 �platinum to IEC 751 (Minco ele-ment code PD or PE).

ThermocouplesA thermocouple consists of twowires of dissimilar metals weldedtogether into a junction. At the otherend of the signal wires, usually aspart of the input instrument, isanother junction called the referencejunction. Heating the sensingjunction generates a thermoelectricpotential (emf) proportional to thetemperature difference between thetwo junctions. This millivolt-levelemf, when compensated for theknown temperature of the referencejunction, indicates the temperature atthe sensing tip. Published millivolttables assume the reference junctionis at 0°C.

Thermocouples are simple and fa-miliar. Designing them into systems,however, is complicated by the needfor special extension wires and refer-ence junction compensation.Thermocouple advantages include:� Extremely high temperature capa-

bility: Thermocouples with pre-cious metal junctions may be ratedas high as 1800°C (3272°F).

� Ruggedness: The inherent simplic-ity of thermocouples makes themresistant to shock and vibration.

� Small size/fast response: Afine-wire thermocouple junctiontakes up little space and has lowmass, making it suitable for pointsensing and fast response. Note,however, that many Minco RTD’shave time constants faster thanequivalent thermocouples.

ThermistorsA thermistor is a resistive devicecomposed of metal oxides formedinto a bead and encapsulate in ep-oxy or glass. A typical thermistorshows a large negative temperaturecoefficient. Resistance drops dramati-cally and non-linearly with tempera-ture. Sensitivity is many times that ofRTD’s but useful temperature rangeis limited. Some manufacturers offerthermistors with positive coefficients.Linearized models are also available.

There are wide variations of perfor-mance and price between thermis-tors from different sources. Typicalbenefits are:� Low sensor cost: Basic thermistors

are quite inexpensive. However,models with tighterinterchangeability or extendedtemperature ranges often costmore than RTD’s.

� High sensitivity: A thermistor maychange resistance by tens of ohmsper degree temperature change,versus a fraction of an ohm forRTD’s.

� Point sensing: A thermistor beadcan be made the size of a pinhead for small area sensing.

Sensor type Temperature rangeSensor

costSystem

costStability

Sensi-tivity

Linearity Specify for:

RTD -260 to 850°C Moderate Moderate Best Moderate BestGeneral purpose sensingHighest accuracyTemperature averaging

Thermocouple -270 to 1800°C Low High Low Low Moderate Highest temperatures

Thermistor -80 to 150°C (typical) Low Moderate Moderate Best PoorBest sensitivityNarrow ranges (e.g. medical)Point sensing

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Choosing Sensor Elements

RTD element typesPlatinum is the most widely specified RTD element type, due to its wide temperature range, stability, and standardization be-tween manufacturers. Copper, nickel, and nickel-iron can offer comparable accuracy at lower cost in many applications.

Elementmaterial

Temperaturerange

Resistivity(� per circular mil

foot at 20°C)Benefits

Typical baseresistance

Sensitivity(Avg. � /°C,0 to 100°C)

TCR�����C

Platinum-260 to 850°C-436 to 1562°F

63.8Greatest rangeBest stabilityGood linearity

100 � at 0°C

1000 � at 0°C

0.393.90

0.00375 to0.003927

Copper-100 to 260°C-148 to 500°F

10.7 Best linearity 10 � at 25°C 0.04 0.00427

Nickel-100 to 260°C-148 to 500°F

41.5Low costHigh sensitivity 120 � at 0°C 0.81 0.00672

Nickel-iron-100 to 204°C-148 to 400°F

120.0Low costHighest sensitivity

604 � at 0°C

1000 � at 70°F

2000 � at 70°F

3.134.799.58

0.00518 to0.00527

RTD and thermistor interchangeabilityThe tables below show temperature tolerance—the allowable deviation from nominal curves—for RTD’s and thermistorsin this catalog. Minco can supply sensors with tighter overall tolerance, or with the narrowest tolerance at a point otherthan 0°C.

Temperature°C

Platinum RTD

±0.06% at 0°C ±0.1% at 0°C ±0.22% at 0°C ±0.36% at 0°C ±0.5% at 0°C ±0.1% at 70°F ±0.24% at 70°F

-200-100

020

100200260300400500600700800850

±0.55°C±0.35°C±0.15°C±0.19°C±0.35°C±0.55°C±0.67°C±0.75°C±0.95°C±1.15°C±1.35°C

±1.3°C±0.8°C±0.3°C±0.4°C±0.8°C±1.3°C±1.6°C±1.8°C±2.3°C±2.8°C±3.3°C±3.8°C±4.3°C±4.6°C

±1.3°C±0.5°C±0.7°C±1.8°C±3.1°C±3.7°C

±0.9°C±1.3°C±2.3°C±3.7°C±4.6°C

±2.1°C±1.7°C±1.3°C±1.6°C±2.9°C±4.4°C±5.5°C

±0.3°C±0.3°C±0.7°C±1.3°C

±0.7°C±0.6°C±1.1°C±1.8°C

Temperature°C

Copper RTD Nickel RTD Nickel-iron RTD Thermistor

±0.2%at 25°C

±0.5%at 25°C

±0.3%at 0°C

±0.5%at 0°C

±0.26%at 0°C

±0.5%at 0°C

±0.5%at 25°C

±0.12%at 70°F

±0.25%at 70°F

±1.0% at 0°C

-1000

20100150200260

±1.5°C±0.7°C±0.5°C±1.5°C±2.2°C±2.8°C±3.6°C

±2.2°C±1.5°C±1.3°C±2.5°C±3.3°C±4.1°C±5.1°C

±0.5°C±0.8°C±1.8°C±2.5°C±3.1°C±3.4°C

±0.8°C±1.2°C±2.2°C±3.0°C±3.7°C±4.0°C

±0.6°C±0.8°C±1.7°C±2.3°C±2.9°C

±2.5°C±1.1°C±1.4°C±2.4°C±3.1°C±3.8°C

±2.9°C±1.4°C±1.2°C±2.2°C±2.9°C±3.6°C

±0.5°C±0.3°C±1.1°C±1.6°C±2.1°C

±1.4°C±0.7°C±2.0°C±2.9°C±3.8°C

±0.2°C±0.2°C±0.3°C±1.0°C

Thermocouple limits of error per ANSI-MC96.1-1982

Junction type:E

Chromel-constantanJ

Iron-constantanK

Chromel-alumelT

Copper-constantan

Limits of error:±1.7°C or ±0.5%

0 to 900°C±2.2°C or ±0.75%

0 to 750°C±2.2°C or ±0.75%

0 to 1250°C±1.0°C or ±0.75%

0 to 350°C

Page A-12 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102

Specifications for Temperature Sensors

Listed below are national and inter-national specifications for RTD’s andthermocouples.

IEC Publication 751Issued by: InternationalElectrotechnical CommissionDate: 1983IEC 751 has the widest internationalscope of any RTD standard. It callsfor platinum RTD’s, 100 � at 0°C,TCR 0.00385 �/�/°C, in one of twotolerance classes:Class A: ±0.06% at 0°CClass B: ±0.12% at 0°CAll Minco RTD’s with PD elementcode meet Class B. Selected modelshave Class A as an option.

DIN 43760Issued by: Deutsches Institut fürNormung (Germany)Date: 1987Specifies resistance curves and toler-ance for nickel RTD’s. Platinumcurves are now covered underIEC 751.

BS 1904:1984Issued by: British Standards Institu-tionDate: 1984Identical to IEC 751.

JIS C 1604-1989Issued by: Japanese Standards Asso-ciationDate: 1989Specifies 100 � 0.00385 platinumthermometers in accordance withIEC 751, but also makes provisionfor 0.003916 TCR. Minco can supplyRTD’s to either curve.

MIL-T-24388C(SH)Issued by: U.S. Naval Sea SystemsCommandDate: 1990RTD’s and thermocouples for ship-board use. Included are platinumRTD’s with 0.00392 TCR and nickelmodels with 0.00672 TCR. See Sec-tion G for bearing embedment RTD’squalified to this specification. Mincodoes not currently offer probe andthermowell models to MIL-T-24388.

SAMA RC21-4-1966Issued by: Scientific ApparatusMakers AssociationDate: 1966Specifies various curves for platinum,nickel, and copper RTD’s. The plati-num curve, available from Minco,has a resistance of 98.129 � at 0°Cand TCR of 0.003923. Placing a fixedresistor of 1.871 � in series with thiselement makes it fit the IEC 751curve.

ANSI-MC96.1-1982Issued by: Instrument Society ofAmericaDate: 1982Sets general standards forthermocouples, including millivolt ta-bles, limits of error, and color codingof wires. All Minco thermocouplesconform to this specification.

ITS-90Issued by: Comité International desPoids et MesuresDate: 1990ITS-90 is the fundamental definitionof temperature itself. It specifies thetemperature in Kelvins of variousphysical constants such as the triplepoint of water. ITS-90 also names theinterpolating instruments to be usedbetween the fixed points. Minco lab-oratory thermometers in section 12meet ITS-90 requirements for resis-tance ratio and calibration, but donot have the stability required forprimary standards. They are suitable,however, for use as secondary trans-fer standards.

Quality standardsMinco’s quality and inspection sys-tems meet MIL-Q-9858 andMIL-I-45208.

What is Temperature Coefficient of Resistance (TCR)?Temperature coefficient differentiatesbetween resistance/temperaturecurves of RTD’s. It is also calledalpha (�) and may be specified invarious ways by different manufac-turers.

In this bulletin TCR is the RTD’s re-sistance change from 0 to 100°C, di-vided by the resistance at 0°C, di-vided by 100°C:

TCR( / / C)R R

R 100 C

100 C 0 C

0 C� � � �

�

� �

� �

�

For example, a platinum thermome-ter measuring 100 � at 0°C and139.11 � at 100°C has TCR0.00391 �/�/°C:

TCR139.11 100

100 100 C0.003911�

�

� ��

� �

�

For a copper RTD, 10 � at 25°C,TCR is:

TCR12.897 9.035

9.035 100 C0.00427�

�

� ��

� �

�

Stated another way, TCR is the aver-age resistance increase per degree ofa hypothetical RTD measuring 1 � at0°C.

The most common use of TCR is todistinguish between curves forplatinum, which is available withTCR’s ranging from 0.00375 to0.003927. The highest TCR indicatesthe highest purity platinum, and is

mandated by ITS-90 for standardplatinum thermometers.

There are no technical advantagesof one TCR versus another in practi-cal industrial applications. 0.00385platinum is the most popular world-wide standard and is available inboth wire-wound and thin-film ele-ments.

In most cases, all you need toknow about TCR is that it must beproperly matched when replacingRTD’s or connecting them to instru-ments.

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RTD Connections: 2-Wire, 3-Wire, 4-Wire?

Because an RTD is a resistance typesensor, resistance introduced by con-necting extension wires between theRTD and control instrument will addto readings. Furthermore, this addi-tional resistance is not constant butincreases with ambient temperature.

To estimate leadwire error in2-wire circuits, multiply the totallength of the extension leads timesthe resistance per foot in the tablebelow. Then divide by the sensitivityof the RTD, given in the next twopages, to obtain an error figure in°C. For example, assume you haveconnected 100 feet of AWG 22 wiresto a 100 � platinum RTD (PD ele-ment). Lead resistance is:

� � R ft ft� � �200 0 0165 3 3. . / . .� �

Approximate error is:

E ��

� �3 3

0 3858 6

.

. /.

�

� CC

Leadwire AWG Ohms/ft. at 25�C

1214161820

2224262830

0.00160.00260.00410.00650.0103

0.01650.02620.04180.06660.1058

You can reduce leadwire error by:� Using larger gauge extension

wires.� Specifying an RTD with greater

sensitivity; 1000 � instead of100 �, for example.

� Employing a 3 or 4-wire resistancecanceling circuit as shown at right.Common leads, connected to thesame end of the sensing element,are the same color.

� Using a 2-wire current transmitter.Its linearized signal is immune toelectrical noise as well as resis-tance and can maintain accuracyover runs of several thousand feet.See Section E for transmitters.

2-wire circuitShown above is a 2-wire RTD connected to a typical Wheatstone bridge cir-cuit. ES is the supply voltage; EO is the output voltage; R1, R2, and R3 are fixedresistors; and RT is the RTD. In this uncompensated circuit, lead resistances L1and L2 add directly to RT.

3-wire circuitIn this circuit there are three leads coming from the RTD instead of two. L1and L3 carry the measuring current while L2 acts only as a potential lead. Nocurrent flows through it while the bridge is in balance. Since L1 and L3 are inseparate arms of the bridge, resistance is canceled. This circuit assumes highimpedance at EO and close matching of resistance between wires L1 and L3.Minco matches RTD leads within 5%.

4-wire circuit4-wire RTD circuits not only cancel leadwires but remove the effects of mis-matched resistances such as contact points. A common version is the constantcurrent circuit shown above. IS drives a precise measuring current through L1and L4. L2 and L3 measure the voltage drop across the RTD element. EO musthave high impedance to prevent current flow in the potential leads. 4-wire cir-cuits may be usable over longer distances than 3-wire, but you should con-sider using a transmitter in electrically noisy environments.

If necessary you can connect a 2-wire RTD to a 3-wire circuit or 4-wire circuit,as shown above. As long as the junctions are near the RTD, as in a connectionhead, errors are negligible.

R1

L1

RT

ES

R2

EO

R3

L2

R1

L1

RT

ES

R2

EO

R3

L2

L3

L1

L2

L3

RTEOIS

L4

RT

RT

RTD leads

RTD leads

Extension leads

Extension leads

Page A-14 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102

Resistance/Temperature Tables

Complete tables in 1°C or 1°F increments are available from Minco at www.minco.com/sensorcalc.

Platinum elements

Element code:Resistance at 0°C:

TCR (�����C)

PJ25.5 �

.00392

PA100 �

.00392

PB100 �

.00391

PD, PE100 �

.00385

PN200 �

.00385

PL470 �

.00392

PH500 �

.00392

PP500 �

.00391

PG500 �

.00385

PF1000 �

.00385

PW1000 �

.00375

PS10k �

.00385

Sensitivity(Average �/°C)

0.100 0.392 0.391 0.385 0.770 1.845 1.963 1.955 1.925 3.850 3.750 38.50

Temperature (°C) Resistance (ohms)

-200-180-160-140-120

-100-80-60-40-20

020406080

100120140160180

200220240260280

300320340360380

400420440460480

500520540560580

600620640660680700

720740760780800

820840850

4.336.568.75

10.9113.05

15.1717.2719.3521.4123.46

25.5027.5329.5431.5433.53

35.5137.4839.4341.3743.31

45.2247.1349.0250.9152.78

54.6456.4858.3260.1461.95

63.7565.5467.3169.0770.83

72.5674.2976.0177.7179.40

81.0882.7584.4086.0487.6789.29

17.0025.7234.3142.8051.19

59.4967.7175.8783.9692.01

100.00107.95115.85123.70131.50

139.26146.97154.64162.25169.82

177.35184.82192.25199.64206.97

214.26221.50228.70235.85242.95

250.00257.01263.97270.88277.75

284.57291.34298.06304.74311.37

317.96324.49330.98337.43343.82350.17

17.2625.9734.5443.0151.37

59.6467.8375.9684.0392.04

100.00107.92115.78123.60131.38

139.11146.79154.42162.01169.55

177.04184.49191.89199.24206.55

213.81221.02228.19235.31242.38

249.41256.39263.32270.21277.04

283.84290.58297.28303.93310.54

317.09323.60330.07336.49342.86349.18

18.5227.1035.5443.8852.11

60.2668.3376.3384.2792.16

100.00107.79115.54123.24130.90

138.51146.07153.58161.05168.48

175.86183.19190.47197.71204.91

212.05219.15226.21233.21240.18

247.09253.96260.79267.56274.29

280.98287.62294.21300.75307.25

313.71320.12326.48332.79339.06345.28

351.46357.59363.67369.71375.70

381.65387.55390.48

37.0454.1971.0987.75

104.22

120.51136.65152.66168.54184.32

200.00215.59231.08246.48261.79

277.01292.14307.17322.11336.96

351.71366.38380.95395.42409.81

424.10438.30452.41466.43480.35

494.18507.92521.57535.12548.59

561.96575.23588.42601.51614.51

627.42640.23

79.88120.88161.28201.15240.57

279.58318.23356.57394.63432.43

470.00507.35544.47581.38618.06

654.53690.77726.79762.59798.18

833.54868.68903.59938.29972.77

1007.031041.061074.881108.471141.85

1175.001207.931240.641273.141305.41

1337.461369.281400.891432.281463.45

1494.391525.121555.621585.911615.971645.81

84.98128.59171.57213.99255.93

297.43338.55379.53419.82460.03

500.00539.73579.23618.49657.51

696.31734.86773.18811.27849.12

886.74924.12961.27998.18

1034.86

1071.311107.511143.491179.231214.73

1250.001285.031319.831354.401388.73

1422.831456.691490.311523.701556.86

1589.781622.471654.921687.141719.12175 0.87

86.30129.84172.72215.03256.83

298.19339.17379.80420.13460.19

500.00539.58578.92618.02656.90

695.54733.94772.11810.05847.75

885.22922.46959.46996.22

1032.76

1069.061105.121140.951176.551211.91

1247.041281.941316.601351.031385.22

1419.181452.911486.401519.661552.68

1585.471618.021650.351682.431714.291745.91

92.60135.48177.72219.38260.55

301.28341.63381.64421.35460. 80

500.00538.96577.70616.21654.48

692.53730.34767.92805.27842.39

879.28915.94952.36988.56

1024.52

1060.261095.761131.031166.071200.88

1235.461269.811303.921337.811371.46

1404.891438.081471.041503.771536.27

1568.541600.58

185.20270.96355.43438.76521.10

602.56683.25763.28842.71921.60

1000.001077.941155.411232.421308.97

1385.061460.681535.841610.541684.78

1758.561831.881904.731977.122049.05

2120.522191.522262.062332.142401.76

2470.922539.622607.852674.622742.93

2808.782876.162942.083007.543072.54

3137.083201.16

846.57923.55

1000.001075.961151.441226.441300.96

1375.001448.561521.631594.221666.33

1737.961809.111879.781949.962019.67

2088.892157.632225.892293.672360.96

2427.782494.112559.962625.332690.22

2754.63

1,8522,7103,5544,3885,211

6,0266,8337,6338,4279,216

10,00010,77911,55412,32413,090

13,85114,60715,35816,10516,848

17,58618,31919,04719,77120,490

21,20521,91522,62123,32124,018

24,70925,39626,07826,75627,429

28,09828,76229,42130,07530,725

31,371

Intr

od

ucti

on

Bulletin TS-102 Stock Order Desk: 1-763-571-3123 Fax: 1-763-571-9142 Web: www.minco.com Page A-15

Copper Nickel Nickel-iron Thermistors

Element code:Base resistance:

TCR (���/°C)

CA10 � at

25°C

.00427

NA120 � at

0°C

.00672

FA604 � at

0°C

.00518

FB1000 �

at 70°F

.00527

FC2000 �

at 70°F

.00527

TA2252 �

at 25°C

R

R

25

125

29 2� .

TB10K � at

25°C

R

R

25

125

23 5� .

Sensitivity(Average ���C)

0.039 0.806 3.133 4.788 9.576 -72 -287

Temperature (°C) Resistance (ohms)

-100-80-60-40-20

020406080

100120140160180

200220240260

5.1285.9236.7127.4908.263

9.0359.807

10.58011.35212.124

12.89713.66914.44215.21715.996

16.77617.55518.33519.116

66.6079.6292.76

106.15

120.00134.52149.79165.90182.84

200.64219.29238.85259.30280.77

303.46327.53353.14380.31

372.79410.73452.82499.06549.46

604.00660.97720.79783.45848.97

917.33988.54

1062.601139.501219.26

1301.86

826.90

908.40995.04

1086.491182.501282.83

1387.211495.421607.181722.261840.41

1961.38

1653.81

1816.811990.092172.992365.012565.66

2774.442990.843214.373444.543680.84

3922.77

1660 K316.5 K75.79 K21.87 K

735528141200560.3282.7

152.887.753.0

3558 K845.9 K239.8 K78.91 K

29.49 K12.26 K559227601458

816.8481.8297.2

Resistance/temperaturecalculationsMost RTD tables follow theCallendar-Van Dusen equation orsome variation thereof:

�Rt � � � �R At Bt Ct02 31

where Rt is the resistance at tem-perature t, R0 is the ice point re-sistance, and A, B, and C are co-efficients describing a giventhermometer.

Request Application Aid #18for a complete set of equationsand coefficients for numericalcalculation of resistance vs tem-perature.

SensorCalc programRTD and thermocouple tablesare available on-line atwww.minco.com/sensorcalc.You can create and store tablesin a variety of formats. You canalso enter resistances and coeffi-cients for custom tables, usingCallendar-Van Dusen or ITS-90equations.

Thermocouples

Junction type:

EChromel-Constantan

+ –Purple Red

JIron-Constantan

+ –White Red

KChromel-Alumel

+ –Yellow Red

TCopper-Constantan

+ –Blue Red

Sensitivity (mV/°C): 0.063 0.053 0.041 0.043

Temperature (°C) Millivolts

-200-150-100

-50

050

100150

200250300350

400450500550

-8.824-7.279-5.237-2.787

0.0003.0476.3179.787

13.41917.17821.03324.961

28.94332.96036.99941.045

-7.890-6.499-4.632-2.431

0.0002.5855.2688.008

10.77713.55316.32519.089

21.84624.60727.38830.210

-5.891-4.912-3.553-1.889

0.0002.0224.0956.137

8.13710.15112.20714.292

16.39518.51320.64022.772

-5.603-4.648-3.378-1.819

0.0002.0354.2776.702

9.28612.01114.86017.816

20.869

Page A-16 Minco Sales: 1-763-571-3121 Fax: 1-763-571-0927 Web: www.minco.com Bulletin TS-102