TECH TIPS - Extech Instruments

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What is a Digital MultiMeter?
A Digital MultiMeter, or DMM, is an electrical test
device that can measure more than one electrical
signal type. Test leads are used to connect to the
device or circuit under test. The meter accepts the
signal and displays the reading in the appropriate
range and unit of measure.
What is the significance of True RMS in a DMM?
A True RMS Multimeter more accurately measures AC
(alternating current) signals. When measuring distorted
or non-periodic AC waveforms, True RMS meters
are essential. Standard meters, without True RMS,
average the AC measurements and therefore are not
as accurate for AC.
Auto Range vs. Manual Range
An autoranging multimeter automatically displays a
reading with the proper decimal place location and
maximum resolution. Manual range meters, as the
name suggests, requires that the user select the
decimal point location and the proper resolution
manually, typically using a rotary select switch.
TECH TIPS
Digital MultiMeters
Double molded for rugged,
waterproof (IP67) protection
Where are MultiMeters used?
MultiMeters are so prevalent today, in all fields
of endeavor, that a comprehensive list would be
impractical in this limited space. However, here are a
few areas of application:
• Communication and Information Technology
installation, test, and maintenance
Field service technicians and engineers
EX530
IR Thermometer with built-in laser! Built-in Non-Contact Voltage Detector
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for appliances, computer systems,
and other machinery
Automotive repair and diagnostics
QA/QC departments for product
test and inspection
Process control technicians and supervisors
Research & development laboratories
Plant maintenance engineers
3rd party and in-house calibration labs
Electrical contractors
Drop-proof to 6 feet (2.9m)
automatically detects a live wire
EX470

What is a clamp meter?
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 allowing the technician to make the
measurement quickly and safely.
Why True RMS Clamp-ons?
A True RMS clamp meter more accurately measures
AC (alternating current) signals. When measuring
distorted or non-periodic AC waveforms, True RMS
meters are essential. Standard meters, without True
RMS, average the AC measurements and therefore are
not as accurate for AC.
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Clamp Meters
Built-in IR Thermometer for quick
and safe non-contact temperature
measurements. Find hot spots fast!
Applications for True RMS Clamp-On Meters
• Power utility personnel for installation,
maintenance, and diagnostics.
• Electrical contractor supervisors and
engineers and electrical journeymen
• Building and facility maintenance
technicians and supervisors
• Manufacturing technicians and floor supervisors
• Technicians for avionic electrical generation
systems and ground support equipment
Current Clamp Meters with DMM functionality
Extech leads the market in multifunction current clamp
meters. In the presence of high current flow, the need
to measure volts, ohms, temperature, and frequency
is imperative. Multifunction current clamp meters offer
a value-added bonus for technicians, field engineers,
and contractors.
What is the significance of the IR thermometer?
In areas where there are high current carrying
conductors, safety is of utmost concern. With an
IR thermometer built right into the clamp meter the
technician can quickly and safely scan for ‘hotspots’
on panels, conduits, and walls.
EX830 EX623
EX600 Series 5-in-1 meters feature built-in dual
True RMS meter gives you accurate
thermocouple inputs for T1, T2, and T1-T2 differential readings of non-sinusoidal
temperature measurement.
waveforms.

What is an Infrared Thermometer?
An Infrared or ‘IR’ Thermometer is an instrument that
can remotely sense the temperature of a surface and
display that temperature digitally.
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.
What are the Advantages of an IR Thermometer?
• Non-Contact measurements are
convenient and safe
• IR measurements are extremely fast
• IR thermometers can measure moving objects
• IR thermometers measure from a safe distance
What is Field of View or
Distance to Spot (D/S) ratio?
The IR sensor beam can be thought of as the beam
of a flashlight; the closer a flashlight is to a wall,
the smaller the light spot; the further from the wall,
the larger the spot. If the D/S ratio of a given IR
thermometer is 10:1, the spot will be a 1” diameter
circle when the meter is held 10” from the surface. At a
20”distance the spot will be 2” in diameter, and so on.
The surface being measured should always be larger
than the spot size for accurate measurements.
Max hold indicates and holds the peak
temperature for easy identification
of hot spots
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TECH TIPS
IR Thermometers
Two laser points converge at a
distance of 30”/76.2cm (model
42512) or 12”/30.5cm (model 42511)
and form a 1” (2.5cm) spot.
Technical Definition of Emissivity
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.
Real World Discussion of Emissivity
Emissivity is not of any concern when the surface
under test is coated by flat black paint (known as a
black body). A black body is considered the maximum
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 considered 1.0 (this
is maximum emissivity). All values of emissivity fall
between 0.0 and 1.0. Many infrared thermometers
have a fixed emissivity of 0.95 which covers most
materials. In the case of a very low emissivity, it is
recommended to apply black paint or tape to the
surface to effectively change the surface emissivity.
42512 42510A IR201

Alternate Terms for Tachometers
• Angular Speed Meter
• Rotation Meter
What is a tachometer?
A tachometer is a device that measures the angular
speed of a rotating shaft in revolutions per minute
(RPM). A good example of a device that can be
measured with a tachometer is a moving fan. Also,
some tachometers can measure linear surface speed
in terms of feet per minute (ft/min) or meters per
minute (m/min). An example of a linear surface speed
measurement is a conveyor belt or escalator hand-rail.
How to select an Extech Tachometer
Use a non-contact (photo) tachometer for applications
where it is not feasible to have the tachometer come
in contact with the rotating device. This is the case in
high speed applications and where the object to be
measured cannot be easily reached.
Use a contact tachometer for applications where direct
contact of the tachometer with the object is preferred.
You can also purchase a combination (contact/noncontact)
tachometer for the maximum in flexibility.
How do Non-contact Tachometers Operate?
Non-contact tachometers use light (photo) reflections
to measure RPM. First, a small piece of reflective
tape (approx. 1/4”) is mounted on the object to be
measured. Second, the light source is directed toward
the tape. The reflection from the tape allows the meter
to measure and display an accurate RPM reading
Accessory wheels enable
tachometer to measure linear
surface speeds
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Tachometers
TECH TIPS
How do Contact Tachometers Operate?
To measure RPM with a contact tachometer, the
tip of the tachometer’s sensor is placed in direct
contact with the rotating object. After a short time an
accurate reading is displayed. Linear surface speed
can be measured in a similar way; a wheel attachment
is connected to the sensor tip and touched to the
moving belt. Three attachment accessories are
provided: Disc, Conical, and Wheel.
What is the significance of an IR Thermometer?
In addition to saving time and cutting cost, the built-in
IR thermometer permits the user to check for hot spots
or to check surface temperature. The IR thermometer
permits non-contact temperature measurements for
areas difficult to reach or unsafe to touch.
Tachometer Applications
• Rotational motor speed
• Moving fans, pumps, gears, and machinery
• Production and automotive use
• Propeller devices
Non-contact model for use on
machinery where high speed
measurements are required
461920 RPM10

Alternate Terms for Tachometers
• Alternate Terms for Anemometers
• Air Flow Meters
• Air Velocity or Wind-speed Meters
• Wind cups or weathervanes
What is an Anemometer?
Anemometers measure the speed (velocity) of moving
air. Thermo-Anemometers also measure temperature
by way of a thermometer located in the Anemometer
sensor. The measurement units for Anemometers
include: Feet per minute (ft/min), meters per second
(m/s), kilometers per hour (km/hr), miles per hour
(mph), nautical miles per hour (knots), and Beauforts.
How does an Anemometer measure moving air?
Anemometers measure moving air with a rotary sensor
which acts very much like a weathervane and can be
likened to the blades of a fan. The vane freely rotates
in response to air flow and as the air moves through
the vane the blades turn in proportion to the speed
of the air.
What is CFM / CMM?
Cubic Feet per Minute (CFM) or Cubic Meters
per Minute (CMM) are units of measure for Air
Volume measurements. This is a measurement
of the quantity of moving air through an air duct,
passageway, or enclosure. In order to accomplish
this, the area of the duct must be measured. The
area value (in ft 2 or m 2 ) is entered by the user by
pushbutton or keypad into the meter and an air
velocity measurement is taken. The meter then
calculates the CFM or CMM automatically.
Built-in non-contact
IR Thermometer
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TECH TIPS
Anemometers
What is the significance of a built-in IR
thermometer?
Having an IR thermometer as part of an Anemometer
offers the user several important benefits:
• Two tools in one
• Save time and cost
• Check for hot spots in duct work, electrical panels,
and wiring conduits
Typical Anemometer Applications
• Air duct measurements
• Positive pressure tests in clean rooms
• Fume hood testing and verification
• Automobile engines analysis
• Automobile passenger compartment tests
• Ionizer flow output monitoring
• Ventilation system inspection
Used in HVAC applications measuring airflow
from heating vents.
HD300
AN200

What are Moisture Meters?
Moisture Meters sense, measure and display the
moisture content of wood and other building products.
Materials such as sheet rock, wall board, mortar,
concrete, plaster, cardboard, and others can be tested
for moisture.
How are Moisture Meters used?
Moisture Meters are used to detect moisture in wood,
wall board, and other building materials to gage
damage from flooding, high humidity, or other causes,
for example. Moisture meters are also used in furniture
manufacturing and rebuilding, wood flooring, wood
drying, flood insurance claims, building inspection,
pest control, and many others.
MO280
Non-invasive Pinless
technology
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TECH TIPS
Moisture Meters
MO290
How do Moisture Meters operate?
Moisture meters determine the moisture content of
a material by way of pin-like probes that are inserted
directly into the material under test. The moisture
reading is then displayed on the meter. The unit of
measure for moisture content varies from instrument
to instrument some use ‘%’ and others use a relative
scale from 0 to 100 where 100 represents maximum
and 0 represents minimum moisture. Many meters also
use a Dry, Moist, and Wet indicator for convenience.
MO280-KW
Pin Moisture Probe included for making
contact moisture measurements

What are Electrical Testers?
Electrical testers are a family of products that can
detect the presence of voltage and/or current
quickly and easily. Electrical testers are portable
and ergonomic, allowing the user to safely hold the
instrument near the source of electricity for testing.
Electrical testers can detect AC only, DC only, or both
AC and DC signals. Some testers can also provide
continuity and phase tests.
Contact and Non-Contact Electrical Testers
There are two types of testers: Contact and Non-
Contact. Contact testers, as the name implies, have
probes that must physically come in contact with the
signal under test in order to make a measurement.
Non-contact devices detect the electrical signal
through magnetic induction and therefore do not need
a physical connection to make a measurement.
AC and DC Electrical Testers
The most common testers measure AC signals. AC
(alternating current) is the power that is provided by
utility companies to homes, offices, and manufacturing
plants. AC signals are present at breaker panels,
wall outlets, switches, light fixtures, etc. DC testers
(direct current) are geared toward the measurement of
low voltage signals associated with battery powered
circuits.
Built-in IR Thermometer with
LCD displays non-contact
temperature measurements
Literature Order Form
TECH TIPS
Electrical Testers
How are Electrical Testers used?
Electrical Testers detect the presence of voltage or
current at an outlet, power strip, light fixture, wall
switch, or any location where electricity may be
present. The user places the tester near (in the case
of a non-contact tester) or in touch with (in the case of
a contact tester) an electrical circuit. The tester may
provide the measurement results audibly, visually, or
by both means. Audible detection is usually by way
of chirping tones that grow louder and more insistent
as the electricity amount increases. Visual alerts
can be simple LED lights or full digital readouts with
bargraphs.
A note about sensitivity adjustments
Many Electrical Testers include a sensitivity
adjustment. Such an adjustment allows the user to
more accurately detect the presence of electricity
by mitigating the possibility of false detection. False
detection can occur when there is a large amount of
static electricity present that triggers the Electrical
Tester. This can confuse the user as to the presence
of electricity in the circuit under test. By adjusting
the tester’s sensitivity, the false triggering can be
minimized.
Quickly check for the presence of live Check voltage in breakerss
wires before testing
DVA30
DV40
VT30

What is a Sound Level Alert?
The Extech Sound Level Alert displays sound level
readings on an extra large LCD ideal for viewing from a
distance. Sound level is displayed in db (decibels) and
also represented by bright, color-coded status LEDs.
The user can program a sound level limit that when
exceeded will change the LEDs from green to flashing
red and display an ‘OVER’ message.
How are Sound Level Alerts used?
The Sound Level Alert can be placed in auditoriums,
hospital wards, class rooms, and other school areas.
When the noise level reaches a predetermined alarm
level, the alert LEDs will warn the occupants. The relay
output permits the user to connect an external audio
or visual device for more dramatic, customized alerts.
What is a Sound Level Datalogger?
The HD600 Datalogging Sound Level meter measures,
displays, and stores sound level measurement data.
Up to 20,000 readings can be stored in the meter,
each with the date and time stamp. Readings can
be recalled on the meter’s display or they can by
downloaded to a PC. Included software permits
the user to view, graph, print, and export data
to a spreadsheet.
How are Sound Level Dataloggers used?
Since a Sound Level Datalogger can automatically
store readings at a user-programmable sample rate,
they are the ideal tool for taking readings ‘unattended’
for long periods of time. After readings are stored
they can be transferred to a PC to be viewed,
graphed, printed, or exported to a spreadsheet for
further analysis. This capability can be applied to
many applications such as airport noise analysis,
construction zone monitoring, traffic intersections,
concert venues, environmental impact studies,
and many others.
Literature Order Form
TECH TIPS
ISO 9001:2000 CERTIFIED
Sound Level Meters
What is ‘A’ and ‘C’ Frequency Weighting?
Frequency “weighting” selections allow the user to
choose how the meter will treat sound measurements
over the meter’s specified frequency range. In ‘A’
weighting mode, the meter gives more “weight” to
certain frequencies. In other words, sound levels at
certain frequencies will be boosted or cut (to match
how the human ear responds to sound). “A” weighting
is useful for OSHA compliance testing. The “C”
weighting selection provides a more “flat” response,
meaning that all frequencies are treated basically
the same (no boosting or cutting of sound level). “C”
weighting is suitable for machine analysis
and diagnostics.
What is the significance of FAST / SLOW
Response Time?
Response Time selections refer to how fast or slow
the meter will respond to sound. Most meters have
a slow and a fast selection. “Slow” response is most
often used for hearing conservation/OSHA programs
and is an “averaging” of sound level over time. “Fast”
response is most commonly used for product noise
reduction efforts and can detect quick noise bursts
(For example: fireworks).
“Make Mine an Extech! The HD600 Datalogging Sound Level Meter meets new
IEC 61672-1 Class 2 accuracy standard for OSHA and
other local and national noise ordinances
407732 ”
Extech Instruments Corporation • 285 Bear Hill Road • Waltham, MA 02451-1064 USA
Phone: 1-781-890-7440 • Fax: 1-781-890-7864 • E-mail: sales@extech.com • Internet: www.extech.com
HD600

What is a Hygro-Thermometer?
A hygro-thermometer measures relative humidity
(RH) and temperature. The unit of measure for relative
humidity is percent (the range is 0.0 to 100.0%). 100%
relative humidity is the maximum amount of moisture
that air can hold without condensation. Temperature
is sensed on Extech Hygro-Thermometers by a
thermistor and is displayed in °C or °F.
What is Dew Point?
Dew Point is the temperature at which water vapor
condenses. It is not as common as relative humidity
measurements but has applications in meteorological,
chemical, and electronic assembly areas.
What is a Psychrometer?
A Psychrometer is a Hygro-Thermometer that uses
Wet/Dry Bulb technology. Wet/Dry Bulb is a complex
humidity-temperature measuring technology that
Extech meters simulate using an internal algorithm.
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TECH TIPS
ISO 9001:2000 CERTIFIED
Hygro-Thermometers
The RH490 Precision Hygro-Thermometer
Psychrometer is specifically designed for HVAC
and water damage restoration contractors
Patented non-contact InfraRed
Thermometer technology built
into a Hygro-Thermometer like
the HD500 is perfect for Home
inspection applications.
Hygro-Thermometer Applications
• Semiconductor fabrication clean rooms
• Environmental analysis
• Electronic assembly
• Food processing and serving areas
• Computer and other workstation environments
• Processes requiring gases in manufacturing
• HVAC applications
• Greenhouses
• Flood restoration
Calibration Bottles
Extech offers calibration references for 33% and 75%
relative humidity. The calibration references are small
bottles that accept the humidity sensor. Periodic
calibration is necessary to insure precise readings.
Check the listings for the appropriate reference bottles
for a given meter.
“Make Mine an Extech! RH490 ”
Extech Instruments Corporation • 285 Bear Hill Road • Waltham, MA 02451-1064 USA
Phone: 1-781-890-7440 • Fax: 1-781-890-7864 • E-mail: sales@extech.com • Internet: www.extech.com
HD500