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Click to Select a Training Module Topic Digital MultiMeters Clamp Meters Tachometers IR Tachometers

Digital MultiMeter Training Module
March 2009 Rev. 1.2

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 capability 0V V 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 VAC providing a tenth of a volt ‘resolution’ 120 V = 1 volt resolution 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 II Single Phase receptable connected loads CAT I Electronic Circuits

Voltage Safety Ratings
In addition to Category Ratings, MultiMeters have Voltage ratings For example, CAT II – 600V or CAT III V 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

Clamp Meter Training Module
March 2009 Rev. 1.1

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 A 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 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 II Single Phase receptable connected loads CAT I Electronic Circuits

Voltage Safety Ratings
In addition to Category Ratings, MultiMeters have Voltage ratings For example, CAT II – 600V or CAT III V 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 Thermometer on 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

Tachometer Training Module
March 2009 Rev. 1.0

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

IR Thermometer Training Module
March 2009 Rev. 1.0

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

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’ continued
The 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 Spot 4” 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