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Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 1 of 69
Basics of Digital Meters Utility Applications
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 2 of 69
Understanding the basics
• Basic Electricity• Safety• Analog or Digital• Manual or Auto-ranging• Displays
– Range and Resolution– Icon Symbols– Numerical System
• Basic Measurement– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 3 of 69
• Fluid Dynamics– How water flows
• Electrical Theory– How electricity flows
• Types of Sources– AC vs. DC
– Measuring AC
Basic Electricity
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 4 of 69
Fluid Dynamics to Electrical Theory
• Water Pressure – Pressure created by a pump
or stored in towers
• Flow or Current – The amount of water
flowing through a pipe
• Impedance– Anything that impedes the
flow of current
• Voltage (V)– Pressure applied to the
conductor
• Amperes or Amp (I or A) – Flow of electrons in the
conductor
• Impedance or resistance () – Impedes or resist the flow of
electrons
How water flows
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 5 of 69
AC Source
• Alternating Current (AC)– Most common
– Produced by a generator
– Has a positive and negative component
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 6 of 69
DC Source
• Direct Current (DC)– Stored energy or
derived from AC with electronic rectifier
– Positive component only
– Used to power electronic devices
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 7 of 69
Understanding the Basics
• Basic Electricity
• Safety• Analog or Digital• Manual or Auto-ranging• Displays
– Range and Resolution– Icon Symbols– Numerical System
• Basic Measurement– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 8 of 69
Why should we be Concerned?
• An electrician troubleshooting a live 480V motor control center receives serious second- and third-degree burns from an electric arc. The cause? – Meter was incorrectly
switched to resistance on his multimeter instead of voltage.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 9 of 69
Why should we be Concerned?
• Two electricians are severely burned — one fatally — while testing for voltage in a motor starter. One held the multimeter while the other applied the meter's probes to energized terminals. One electrician's movement caused one test lead banana plug (energized from the circuit under test) to pull loose from the multimeter jack. – The plug made contact with the
starter's grounded metal enclosure and initiated a high-energy arc.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 10 of 69
Common Mistakes Made
• Test Leads in the Current input ports and user mistakenly makes an AC or DC Voltage– In this example there were
two errors made by the end user.
• AC voltage measurement with the Test leads in the current input.
• Improper fuse had been used in the meter from a past error.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 11 of 69
Common Mistakes Made
• Here is what happens.– If the unit is not fused it can lead
to damage of meter or to the operator
– Current inputs are very low resistance. Most current inputs are less that 1 Ω. This is like applying a short to the line.
– For current input protection most DMMs’ are Fused.
– The better ones use high energy fusing.
Current
Protection
Fuse If Voltage is measured, Leads in Current input
Ideal 61-490 series gives a probe error message and High audible warning if this mistake to made
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Common Mistakes Made
• Function Switch in wrong function for attempted measurement– Most common is AC or DC
voltage measurement with meter in the Ohms function
– Most IDEAL meters are Overload Protected and the protected levels are listed in the operation manual.
Ideal 61-700, 61-760 and 61-770 series will give you a Hi-V light and audible warning if
you make this Mistake
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Common Mistakes Made
• Using a meter in an area above its stated rating – Example: 2,300 voltage
measurement with an instrument rated for Low Voltage (600V AC/DC.)
– Overload Protected can not protect you from this Kind of mistake.
– Most Overload protected is rated based on instruments highest voltage measurement rating.
There are Bold Electricians and Old electricians, but not many
Bold-Old ones
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Common Safety Hazards
• Electrical Shock from accidental contact from live electrical circuits or devices– Use double insulated rated
leads – Shrouded input jacks with
finger guards – Test for proper continuity
often.
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Common Safety Hazards
• High Voltage transients from lightning, large inductive loads being switched on and off, or capacitive discharge. – Select meter with the proper
UL/IEC Category rating for the environment that user is going to be working in.
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Certified Devices and Equipment
• Look for tools that are Certificated by an independent lab, – UL , IEC, CSA.
• Pay close attention to the safety rating on the equipment. – Never use equipment that is not
properly rated, Check Sp
• Never use accessories that are not recommended or rated for your tester or environment.
IEC Cat ratings
The New UL 61010 standard incorporates features of the IEC
601010 standard. This standard has improved safety benefits over the old
UL 1244 standard
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 17 of 69
IEC Category Ratings
• If a lighting strike was to hit your electrical service a certain amount of energy or impulse would travel and be dissipated by the electrical service. The closer to the source of the impulse the Higher available fault current.
• IEC 61010 defines as four Categories:– CAT IV “Origin of
installation”, – CAT III Distribution Level, – CAT II Local level, – CAT I Signal Level,
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 18 of 69
Safety Practices
• Visually inspect the test tool.– Check for any contaminate on the test
leads, tester case, holsters, and accessories.
– Never use testers that have signs of cracked cases, or loose components.
– Never use a tester in an environment that is beyond the capabilities described in the specifications
– Use manufactures recommended replacement components, like leads and fuses.
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Safety Practices
• Visually inspect Test Leads– Proper Category rating
– Double insulation
– Shrouded connectors
– Finger guards
– Insulation not damaged: not melted, cut, cracked, stretched
– Connectors: no insulation pulled away from end connectors
– Probe tips: not loose or broken off (too short)
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 20 of 69
Before you get Started
• Whenever possible, work on de-energized circuits. • Use well maintained tools and appropriate safety gear
• Safety glasses, insulated tools, insulating gloves, flash suits, insulating mats, etc.
• Follow proper safety precautions and Lockout /Tag out practices. • Never Work alone when making measurements on live circuits.• Always do a performance test on your tester before making a measurement
on an unknown circuit.– Use the 3 point method. Measure a known test point , Make the unknown
measurement, then back to the known test measurement.– Change battery when indicated – Check test leads regularly
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Before you get Started
• Quick Check of your Test Tool– Digital Multimeter or Digital Clamp meter– Check the Test Leads– Place the DMM in the lowest resistance range and short the Test Leads– Move the test lead at in input of the meter at the ankle of the leads. Watch that the
resistance is less than 0.5 ohms. Do the same at the leads grip and tips. If at any time during this test the resistance exceeds 0.5 ohms the leads my need to be replaced.
• It is also a good Idea to check the DC voltage and Ac voltage with a known source before beginning the day.
– This doesn't negate the “Three point measurement” method.
• If the unit has current, check the Fuse, and remember to replace with only the manufacturer recommended replacement part.
• Remember to always be aware of your battery usage. Digital instruments will become erratic or can give improper readings once the power drops below normal operating levels
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 22 of 69
Know your tester
• Packaging– Material,
• Insulation rating• Environmental rating,
Splash proof or not.• Features
– MIN/MAX, Peak, Hold• Measurement Functions
– AC Volts, DC Volts Capacitance, etc
– Measurement range and Maximum input
– Input protection.• Safety
– CATegory rating, UL, CE
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 23 of 69
Electrical Testers
• Analog solenoid Testers– Very low input impedance – AC Voltage – Continuity testing on some models – Low Accuracy and resolution
• Digital Testers– Low input impedance– AC or DC Voltage – Continuity testing– Good Accuracy and Resolution
• Added Features– NCV (Non-contact Voltage– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 24 of 69
Digital Multimeter and ClampMeter
• Multimeter– Full Voltage ranges – Full Resistance ranges– Low current measurement
through internal shunts
• ClampMeter– One or two Voltage ranges– Limited Resistance ranges– High Current through the
fixed jaw (current transformer) The IDEAL TightSight™
ClampMeter is also a Full functional Digital
Multimeter
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 25 of 69
Understanding the Testers
• Basic Electricity• Safety• Analog or Digital
• Manual or Auto-ranging• Displays
– Range and Resolution– Icon Symbols– Numerical System
• Basic Measurement– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 26 of 69
Function Switch
• Most DMMs have rotary dial to change test functions.
• Manual ranging DMMs– Require manual setting of the range
• Lower cost• Forces you to “think” before testing• Faster response time
• Auto Ranging DMMs– Automatically chooses the range
• Simpler to use
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 27 of 69
Understanding the Testers
• Basic Electricity• Safety• Analog or Digital• Manual or Auto-ranging
• Displays– Range and Resolution– Icon Symbols– Numerical System
• Basic Measurement– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 28 of 69
Display Count
Auto ranging meters will have function symbol– They are also visible on
the LCD Display
Typical displays are 2000 or 4000 counts”
–Ranges on the dial are in series of 2’s or 4’s
–No Function information is displayed.
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Range and Resolution
• Range determines– The maximum reading
– The number of decimal places displayed
• Resolution determines how many digits after the decimal point– Higher resolution = more
decimal places displayed 200V on the 400V Range 0.1V Resolution
200V on the 600V Range 1V Resolution
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 30 of 69
Range and Resolution
If we measure a 240V supply with a 2000 count Meter we would be on the 600V range and read 240V
Range Reading Resolution
600 600 1
200 199.9 .1
20 19.99 .01
2 1.999 .001
200m 199.9 .1mV
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 31 of 69
Range and Resolution
Measure the same 240V supply with a 4000 count Meter you will be on the 400 Range and have one more digit of resolution 240.0V
Range Reading Resolution
600 600 1
400 399.9 .1
40 39.99 .01
4 3.999 .001
400m 399.9 .1mV
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 32 of 69
Measurement Functions
V AC Voltage Measures amount of AC Electrical pressure
V DC Voltage Measures amount of DC Electrical pressure
mV Milli Volts .001V or 1/1,000 V
A Amperes Measures amount of electron flow
mA Milli Amperes .001A or 1/1,000 A
µA Micro Amperes .000001A or 1/1,000,000A
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 33 of 69
Measurement Functions
Ohms Measure of the resistance to electron flow
Diode Device used to control direction of electron flow
)))) Audible Continuity Audible indication of continuity
Capacitance Device used to store electrical potential
HZ Hertz Measurement of Frequency or number of cycles per/sec
°F Degrees Fahrenheit Temperature Measurement
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 34 of 69
Measuring AC
• Average responding meters take a single sample to measure the waveform. – Only accurate where a clean 60Hz
sine wave exists• True RMS meters take several sample
to improve accuracy of measurement– Found in commercial and
industrial environments– Caused by electronic lighting,
computers Equipment and Industrial electronic control loads
– NEC recommends True RMS meters for testing all electrical power systems
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 35 of 69
Term giga mega kilo Base milli micro nanoSymbols G M k m nExpression
X109
X106 X103 X100
X10-3 X10-6 X10-9
Term Numerical value
Giga 1,000,000,000
Mega 1,000,000
kilo 1,000
Term Numerical value
Milli .001
Micro .000001
Nano .000000001
Numerical System
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 36 of 69
Understanding the Testers
• Basic Electricity• Safety• Analog or Digital• Manual or Auto-ranging• Displays
– Range and Resolution– Icon Symbols– Numerical System
• Break • Basic Measurement
– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 37 of 69
Understanding the Testers
• Basic Electricity• Safety• Analog or Digital• Manual or Auto-ranging• Displays
– Range and Resolution– Icon Symbols– Numerical System
• Basic Measurement– DC Volts& AC Volts– Resistance, Capacitance– Current
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 38 of 69
Primary DMM Test Functions
• Voltage (V) - measured in volts– Pressure created by a power supply
• Current (A) - measured in amps– The amount of electricity flowing
through a conductor
• Resistance () - measured in ohms– Anything that impedes the flow of
current
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Taking Measurements
• AC Voltage• DC Voltage• AC Current• DC Current• Resistance• Continuity• Capacitance• Frequency
IDEAL Test Board
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 40 of 69
The Port Panel
• Black lead always placed in Common Port (COM)
• Red lead is placed in Red Port for the function to be measured
• For Voltage connect to the – ( VΩHz) Port
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DC Voltage Measurement
• DC Voltage Measurement• Connect the leads to the
VΩHz and COM inputs• Select VDC or
– If manual ranging select proper range
• For 9V, Select the 20V range
• Measure the 9 Volt battery – If connected to the test board
look for ( + Battery -) test points.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 42 of 69
Parallel Circuit
• In a parallel circuit, Voltage is applied equally to each load connected to the circuit– This is how our
receptacles in our homes are wired. If I change the value
of the resistor in this circuit will it change the voltage across the light???
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 43 of 69
AC Voltage Measurements
• AC Voltage Measurement• Connect leads to the
VΩHz and COM inputs • Select VAC or
– If manual ranging select proper range
• For 120V, Select the 200V Range
• Measure receptacle, or using test points on a line splitter Never make a Voltage measurement with
the leads of the meter in the current input ports
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 44 of 69
Single Phase 3 Wire Meter (Common Residential)Class 100/200 (100/200 Amp)4 Terminal, 240 Volt
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 45 of 69
Single Phase 3 Wire Meter (Common Residential)Class 100/200 (100/200 Amp)4 Terminal, 240 Volt
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 46 of 69
Single Phase 3 Wire Meter (Common Residential)Class 100/200 (100/200 Amp)4 Terminal, 240 Volt
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 47 of 69
Average vs. True RMS
• True RMS responding – The Meter calculates
the true effective (heating) value of the waveform.
– Average sensing meters will not correctly display the effective (heating) value on a “non-sinusoidal waveform.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 48 of 69
True RMS
• Measures the area under the sine wave using a root mean square calculation
• Gives an accurate AC measurement when harmonics are present
• NEC recommends True RMS meters for testing all electrical power systems
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 49 of 69
Current Measurements
• AC Current– Measures the magnetic field around a wire– Converts measurement to an amp reading– Only a single conductor can be tested– Magnetic fields of hot and neutral cancel out– Requires a line splitter in power cords
• DC Current– DC current is measured using a Hall Effect
• An electronic device which measure the EMI of AC and DC current.
Test & Measurement
ClampMeter or Clamp Adapter
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 50 of 69
AC Current Measurement
• AC Current Measurement– Must be made on a single
conductor.
• Plug hairdryer into line splitter
• Plug line splitter into receptacle
• Clamp jaws around line splitter
• Measure the current draw of the hairdryer
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 51 of 69
Series Current Measurement
• In a series circuit, loads within the circuit have an effect on the flow of electricity to the
other devices or loads
If I increase the value of the resistor will it effect the brightness
of light.??
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 52 of 69
Current Measurements
• Requires an open circuit – electrician must interrupt power– Best to us a meter with fused inputs for safety.
• 1 to 10A Max on most DMM’s • Primarily used to measure small Currents
Series Method
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 53 of 69
DC Current Measurement
DC current measurement of a 4 to 20mA control loop
• A break must be made between the transmitter and Controller.
• Place the Test leads in the proper input ports. And select DC mA– 4 mA typically corresponds to
zero – 20 mA typically corresponds to
Full scale.
4-20mA Control Loop
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 54 of 69
Continuity Measurement
• Continuity measurement
• Connect the leads to the VΩHz and COM input port
• Select the continuity function
– Touch leads together
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 55 of 69
“OL” Customer breaker(s) open
“Numerical Value”
Breaker(s) closed
“0.0 to 0.8” SHORT
on customer wiring
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 56 of 69
Resistance Measurement
• Resistance Measurement• Connect the leads to the
VΩHz and COM input port
• Select the Ω ohms Function.– If manual ranging select
proper range
• Measure the Resistor on the Test Board
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 57 of 69
“OL” Customer breaker(s) open
“Numerical Value”
Breaker(s) closed
“0.0 to 0.8” SHORT on customer wiring
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 58 of 69
“OL” Customer breaker(s) open
“Numerical Value”
Breaker(s) closed
“0.0 to 0.8” SHORT on customer wiring
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 59 of 69
Diode Measurement
• Diode measurement• Connect the leads to
the VΩHz and COM input port
• Select the diode function
– Place Red lead on + and black lead on – for “Forward bias”
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 60 of 69
Capacitance
• Function used in testing capacitors– Storage devices that give
motors an initial energy boost
• Capacitance is the ability of a capacitor to hold its charge
• Measured in microfarads (MFD)
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 61 of 69
Capacitance Measurement
• Capacitance Measurement
• Connect the leads to the proper input posts– On some units this isn’t the
Volt/Ohms port
• Select the Capacitance Function , MFD or mF
• Measure the capacitor on the PC board
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 62 of 69
Basic Advanced Features
• Basic of Advance features found on most high end DMM’s and ClampMeters– Hold or Data Hold
– Peak Hold• Peak Min/Max
– Min/Max
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Measurement Functions
• Functions button operation
– Primary Function MIN/MAX press for 1 Second
– Press MIN/MAX To cycle through Max/Min.
• Note display
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Measurement Functions
• To exit a Function– Primacy Function
• Press for 1 second toggles function A”ON”
• Press and hold for 2 seconds toggles function “OFF”
– Secondary Function• Press and hold for >2
seconds toggles function “ON” or “OFF”
• Note display
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 65 of 69
Hold Measurement Functions
• Hold or data hold is used to lock the current measurement reading on the display– While making a
measurement, press the Hold button. Remove test leads and observe the displayed reading.
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Measurement Functions
• Peak Hold Records the Maximum amplitude of a voltage waveform.
• Peak min/max Records the maximum and minimum amplitude of a voltage waveform.
Peak = RMS x 1.414
Example: 169.68= 120V x 1.414
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Min/Max Measurement Functions
• Min/Max Records the minimum and maximum value of a measurement. Each time a new min/max level is achieved the new value will be recorded . – Some DMM will also indicate new recorded values by an
audible beep.
This Function is not fast enough to capture Power Quality Voltage Event.
Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 68 of 69
Voltage Performance Monitor
Key Points for comparison• High speed Even capture
• Only important events are logged
• Events are sorted by Time (log)
• Events are sorted by Type (event)
• Waveform shape is measured for THD
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Clamp-On Ground Resistance Test
• Advantage is that the ground electrode doesn’t need to be disconnected from the electrical system.
• The jaws of the clamp must be placed in the electrical path of the systems grounding wire to the ground rod