© 2007 ideal industries 1 of 69 basics of digital meters- utility applications basics of digital...

Basics of Digital Meters- Utility Applications© 2007 Ideal Industries www.idealindustries.com 1 of 69

Basics of Digital Meters Utility Applications


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


• Fluid Dynamics– How water flows

• Electrical Theory– How electricity flows

• Types of Sources– AC vs. DC

– Measuring AC

Basic Electricity


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


AC Source

• Alternating Current (AC)– Most common

– Produced by a generator

– Has a positive and negative component


DC Source

• Direct Current (DC)– Stored energy or

derived from AC with electronic rectifier

– Positive component only

– Used to power electronic devices


Understanding the Basics

• Basic Electricity

• Safety• Analog or Digital• Manual or Auto-ranging• Displays




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.


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.


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.



• 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



• 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



• 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


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.


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.


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


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,


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.


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)


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


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


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


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


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


Understanding the Testers

• Basic Electricity• Safety• Analog or Digital

• Manual or Auto-ranging• Displays




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



• Basic Electricity• Safety• Analog or Digital• Manual or Auto-ranging

• Displays– Range and Resolution– Icon Symbols– Numerical System



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.


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



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



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


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



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


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


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





• Break • Basic Measurement

– DC Volts& AC Volts– Resistance, Capacitance– Current


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


Taking Measurements

• AC Voltage• DC Voltage• AC Current• DC Current• Resistance• Continuity• Capacitance• Frequency

IDEAL Test Board


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


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.


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???


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


Single Phase 3 Wire Meter (Common Residential)Class 100/200 (100/200 Amp)4 Terminal, 240 Volt


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.


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


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


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


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.??


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


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


Continuity Measurement

• Continuity measurement

• Connect the leads to the VΩHz and COM input port

• Select the continuity function

– Touch leads together


“OL” Customer breaker(s) open

“Numerical Value”

Breaker(s) closed

“0.0 to 0.8” SHORT

on customer wiring


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




Breaker(s) closed

“0.0 to 0.8” SHORT on customer wiring


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”


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)


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


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



• Functions button operation

– Primary Function MIN/MAX press for 1 Second

– Press MIN/MAX To cycle through Max/Min.

• Note display



• 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


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.



• 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


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.


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


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

© 2007 ideal industries 1 of 69 basics of digital meters- utility applications basics of digital...

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