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Digital MultiMeters

Clamp Meters

Tachometers

IR Tachometers

March 2009 Rev. 1.2

Digital MultiMeter Training Module

What is a Digital MultiMeter

A Digital MultiMeter (or DMM) is an

instrument capable of performing a number

of measurement functions and displaying the

results digitally

The basic functions that most meters offer

are Voltage, Current, Resistance, Diode, and

Continuity

Some DMMs offer more advanced functions

such as Capacitance, Frequency, Power, and

Temperature

How are Digital MultiMeters used

To perform tests, meters are connected to circuits,

components, and other devices via 'test leads'

Test leads are insulated wire probes that plug

directly into the meter

Dials or switches on the meter allow the user to

select the measurement function and other

modes of operation

Display icons inform the user as to the unit of measure,

range, resolution and other useful information

Auto Range and Manual Range Meters

On a Manual Range meter, the user must select the

measurement range using a selector switch or rotary

dial

An Auto Range instrument automatically selects the

optimum range and display resolution

Auto Range meters have the added benefit of allowing

Manual Range operation if and when desired

Measurement Range

For a given measurement function, the range refers to

the span between the highest and lowest possible

meter readings. For example, in the AC voltage mode,

a range of 0 to 240VAC means that a measurement of

120VAC is possible because it falls in the “range” of

the meters capability0V 60 120 180

240V Range

Measurement Resolution

For a given measurement function, the resolution refers to

how finely a meter reading can be expressed. For example,

when measuring AC voltage, if the meter’s resolution is 1

volt, a measurement of 120 VAC would display as 120VAC.

However, for a resolution of 0.1 the reading would be

expressed as 120.0 VAC providing a tenth of a volt

‘resolution’

120 V = 1 volt resolution

120.0 V = 0.1 (tenth of a volt) resolution

True RMS vs. Average Responding Meters

An Average Responding meter measures AC signals by

averaging the peaks and valleys of a waveform; This is perfectly

acceptable for periodic, distortion-free sinusoidal signals

However, for non-periodic, noisy, & distorted

waveforms a True RMS meter is needed if

high accuracy is required

True RMS is a ROOT MEAN SQUARE function that maps

instantaneous points along a waveform leading to an accurate

measurement value

Safety Rating Categories

• Hazardous transients and spikes can occur during measurements

• In order to shield the user, meters are outfitted with one of four

protection levels known as Category Ratings (CAT I, II, III, IV)

• The higher the CAT number, the higher the transient protection

• The user selects a Category of meter that is appropriate for the

area where the testing is to be performed

• For example, working with 3 phase motors, variable speed

drives, 277V lighting circuits, or distribution panels requires Cat

III meters

Safety Rating Category Guidelines

CAT IV- 3 phase at utility connection- Outdoor conductors

CAT III- 3 Phase Distribution- Commercial lighting

CAT IISingle Phase receptable

connected loads

CAT IElectronic Circuits

Voltage Safety Ratings

In addition to Category Ratings, MultiMeters have Voltage ratings

For example, CAT II – 600V or CAT III - 1000V

Confusion can arise from these safety conventions. A CAT II –

1000V does not offer more protection than a CAT III – 600V meter

Always refer to the CAT rating first and then the voltage rating

Extech EX300 Series

• Mini Digital MultiMeters + AC Voltage Detector

• Large Digits for easy viewing

• LED indicator & audible tone for Volt Detector

• Manual or Auto Range Models

• Thermometer, Capacitor, and Frequency Models

Extech EX400 Professional Series

• Non-contact IR Thermometers on select models

• Large Backlit Display

• True RMS on select models

• Auto Range on select models

• Low Current Measurement Capability

• Input Fuse Protection

• Incorrect Connection Warnings

• Capacitance, Frequency, Frequency on select models

Extech EX500 Heavy Duty Industrial Series

• Water proof design

• Double molded

• 1000V protection – all functions

• Large Backlit LCD

• True RMS models

• 4,000, 6,000, and 40,000 display count models

• Bargraph on select models

Back to Main Menu

March 2009 Rev. 1.1

Clamp Meter Training Module

What is a Clamp Meter

A Clamp Meter is an instrument capable of

measuring AC or DC Current by clamping

around a single conductor and displaying the

results digitally

Clamp meters oftentimes have Digital

MultiMeter functions built in such as Voltage

and Resistance

The area of the meter that clamps onto the

conductor is known as the ‘jaw’ and is opened

by the user with a press of a button

Clamp Meters continued

A clamp meter is a safe, convenient, and efficient way to

measure current without having to use test leads

Since current flow through a conductor causes a magnetic

field, the clamp meter can sense this field and provide a

corresponding current reading (in amperes or amps)

Clamp meters do not interrupt current flow thereby allowing

the technician to make the measurement quickly and safely.

How are Clamp Meters used

To perform tests the meter is clamped around

a single conductor using the clamp jaw

Dials or switches on the meter allow the user to

select the range and other modes of operation

Display icons convey the unit of measure, range,

resolution and other useful information

If a cable run includes more than one conductor

It must be modified to allow access to only one

conductor at a time

AC Line Separator

An AC Line Separator or

'Splitter' allows the user

to isolate a single

conductor from a multi-

conductor cable safely,

easily, and without the

need for splicing wires

manually.

Auto Range and Manual Range Clamp Meters

On a Manual Range meter, the user must select the

measurement range using a selector switch or rotary

dial

An Auto Range instrument automatically selects the

optimum range and display resolution

Auto Range meters have the added benefit of allowing

Manual Range operation if and when desired

Measurement Range

The range refers to the span between the highest and

lowest possible meter readings. For example, in the AC

Current mode, a range of 0 to 40 Amperes means that

a measurement of 20A is possible because it falls in the

meter's 'range'

0A 10 20 30 40ARange

Measurement Resolution

For a given measurement function, the resolution refers to

how finely a meter reading can be expressed. For example,

when measuring AC Current, if the meter’s resolution is 1

amp, a measurement of 20 amps would display as 20.

However, for a resolution of 0.1 the reading would be

expressed as 20.0 providing a tenth of a volt ‘resolution’

20 A = 1 Amp resolution

20.0 = 0.1 (tenth of a Amp) resolution

True RMS vs. Average Responding Meters

An Average Responding meter measures AC signals by

averaging the peaks and valleys of a waveform; This is perfectly

acceptable for periodic, distortion-free sinusoidal signals

However, for non-periodic, noisy, & distorted

waveforms a True RMS meter is needed if

high accuracy is required

True RMS is a ROOT MEAN SQUARE function that maps

instantaneous points along a waveform leading to an accurate

measurement value

Safety Rating Categories

• Hazardous transients and spikes can occur during measurements

• In order to shield the user, meters are outfitted with one of four

protection levels known as Category Ratings (CAT I, II, III, IV)

• The higher the CAT number, the higher the transient protection

• The user selects a Category of meter that is appropriate for the

area where the testing is to be performed

• For example, working with 3 phase motors, variable speed

drives, 277V lighting circuits, or distribution panels requires Cat

III meters

Safety Rating Category Guidelines

CAT IV- 3 phase at utility connection- Outdoor conductors

CAT III- 3 Phase Distribution- Commercial lighting

CAT IISingle Phase receptable

connected loads

CAT IElectronic Circuits

Voltage Safety Ratings

In addition to Category Ratings, MultiMeters have Voltage ratings

For example, CAT II – 600V or CAT III - 1000V

Confusion can arise from these safety conventions. A CAT II –

1000V does not offer more protection than a CAT III – 600V meter

Always refer to the CAT rating first and then the voltage rating

Extech EX800 Series

• 1000 Amp Clamp Meters with IR Thermometer

• True RMS Current / Voltage on select models

• DMM functions include Voltage, Resistance,Capacitance, Frequency, Diode, and Continuity

• Auto Range

• 1.7" Clamp Jaw Opening

Extech EX700 Double Molded Series

• 800 AC Amp Clamp Meters with Type K Thermometeron select models

• DC Current on Model EX730

• True RMS Current / Voltage on select models

• DMM functions include Voltage, Resistance,Capacitance, Frequency, Diode, and Continuity

• Auto Range

• 1.2" Clamp Jaw Opening

Extech EX600 Series

• 400A Dual Input Clamp Meters with IR

Thermometer and Non-contact volt detector

• True RMS for AC Voltage / Current

• Non-contact voltage detector offers LED alert

• 40,000 display counts for DMM functions

• DMM functions include Voltage, Resistance,

Capacitance, and Frequency

• 1.4" Clamp Jaw Opening

Back to Main Menu

March 2009 Rev. 1.0

Tachometer Training Module

What is a Tachometer

A tachometer measures the angular speed of

a rotating shaft in revolutions per minute

(RPM)

A good example is a rotating fan blade

Some tachometers can measure linear surface

speed in terms of feet (or meters) per minute

For example, a conveyor belt or escalator

hand-rail

Contact Tachometers

The tip of the Contact Tachometer's sensor

is place in direct contact with a moving

object in order to obtain a measurement

reading

The sensor tip can be fitted with a wheel or

other supplied attachment for contacting

shafts, belts, and other moving objects

Use a contact tachometer for applications

where direct contact of the tachometer

with the object is preferred

Non-Contact Photo Tachometers

Non-contact tachometers use light

(photo) reflections to measure RPM

A small square of reflective tape

(approx. 1/4") is mounted on the object

to be measured and the meter's light

source is directed toward the tape

The reflection from the tape allows the

meter to display an accurate RPM

reading

Combination Tachometers

Combination tachometers support Contact

and Non-Contact operation

One end of the meter is a Photo Tachometer

and the other is a Contact Tachometer

The LCD display is typically reversible so

that the user can switch from one mode of

operation to the other and the display will

automatic orient the displayed reading

Laser pointer feature

A laser pointer allows the

user to better aim the

Photo Tachometer

InfraRed (IR) Thermometer Feature

In addition to saving time and cutting

cost, the built-in IR thermometer can

check for hot spots and scan surface

temperature

The IR thermometer permits non-contact

temperature measurements for areas

difficult to reach or unsafe to touch

Extech RPM10

• Combination Laser Tachometer

• Built-in IR Thermometer

• Fixed Emissivity 0.95

• 6:1 distance to spot ratio (IR)

• Automatic Reversible Display

Extech 461920

• Mini Laser Photo Tachometer / Counter

• Non-contact RPM Measurements

• Count Measurements to 99,999 revolutions

• Backlit 5-digit LCD display

• Rugged double molded housing

Extech 461995

• Copmbination Contact / Laser Photo Tachometer

• Non-contact and Contact Measurements

• Reversible LCD display

• Laser guided non contact measurements

• Records last 5 readings

Back to Main Menu

March 2009 Rev. 1.0

IR Thermometer Training Module

What is an InfraRed (IR) Thermometer

In Infrared or ‘IR’ Thermometer is an

instrument that can remotely sense

the temperature of a surface and

display that temperature digitally

The user simply points the meter,

pulls the trigger, and reads the

surface temperature

How does an IR Thermometer work

An IR thermometer senses the infrared

energy emitted by the surface under test

All materials emit infrared energy and the

amount of energy emitted is proportional

to the temperature of the material

The meter simply converts the infrared it

collects into a temperature display

Advantages of an IR Thermometer

Non-contact measurements are safe

IR measurements are extremely fast

IR Thermometers can measure moving objects

IR thermometers can measure from a safe distance

What is ‘Field of View’

The field of view is the area that the meter's sensor

encompasses

This area changes size as the meter is moved closer or further

away from the target

In this way, the IR sensor beam behaves much like a flashlight

The closer a flashlight is to a wall, the smaller the light spot;

the further from the wall, the larger the spot

‘Field of View’ continuedThe Field of view is governed by the meter's 'Distance to Spot ratio'

If the D/S ratio of a given IR thermometer is 12:1, the spot will be a 1” diameter circle when the meter is held 12” from the surface

1”

2”

Distance to Object

Diameter of Spot4”

6”

12”

24”

48”

0.5”

What is Emissivity

Technical Definition

Emissivity is defined as the ratio of the energy radiated by an

object at a given temperature to the energy emitted by a

perfect radiator, or blackbody, at the same temperature

More on Emissivity

Emissivity is not a concern when the surface under test is

coated by flat black paint (black body). Flat black is the highest

emissivity

However, in common practice, surfaces can be highly polished

and very reflective. These are known as low emissivity surfaces.

In these cases the IR thermometer can have difficulty obtaining

an accurate reading. This is where Emissivity comes into play

Many IR thermometers have an adjustable emissivity which

compensates for low emissivity surface characteristics.

Emissivity Settings

The emissivity of a blackbody is 1.0. The full emissivity range is

0.0 to 1.0. The lower the number, the more reflective the

surface

Some meters allow the user to set the emissivity to match the

characteristics of the surface under test

Other infrared thermometers have a fixed emissivity of 0.95

For very low emissivities, flat black paint or tape should be

applied to the surface to effectively change the surface

emissivity

Extech Model 42512

• Dual Laser IR Thermometer

• Dual laser simplifies distance to target ratio

• Exclusive 150ms temperature spike capture

• Adjustable Emissivity

• Adjust High-Low Temperature alerts

• Double molded housing

Extech Model 42542

• High Temperature IR thermometer (1832 degrees F)

• 30:1 D/S ratio

• Adjustable High-Low Temperature Alerts

• Adjustable emissivity

• Large Backlit LCD

• Laser point identifies target area

Extech Model 42560

• IR Thermometer Wireless PC Interface

• 30:1 D/S ratio

• High-Low Temperature Alerts

• Adjustable emissivity

• Large Backlit LCD

• Laser point identifies target area

• Complete with transmission base,

remote USB receiver, software, and more

Back to Main Menu