Extech Instruments 42540a User manual

User’s Manual
High Temperature InfraRed Thermometer
with Laser Pointer
MODEL 42540A
42540
6

Model 42540A V2.1 January 20062
Introduction
Congratulations on your purchase of the Model 42540A IR Thermometer. The 42540A is
capable of non-contact (infrared) temperature measurements at the touch of a button. The
built-in laser pointer increases target accuracy while the backlit LCD and handy push-
buttons combine for convenient, ergonomic operation. This meter is shipped fully tested
and calibrated and, with proper use, will provide years of reliable service.
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and
workmanship for three (3) years from date of shipment (a six month limited warranty applies on sensors and
cables). If it should become necessary to return the instrument for service during or beyond the warranty
period, contact the Customer Service Department at [phone] ext. 210 for authorization or visit our
website at www.extech.com (click on ‘Contact Extech’ and go to ‘Service Department’ to request an RA
number). A Return Authorization (RA) number must be issued before any product is returned to Extech. The
sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in
transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper
wiring, operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech
specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and will not be
liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited to repair or
replacement of the product. The warranty set forth above is inclusive and no other warranty, whether written or
oral, is expressed or implied.
Calibration and Repair Services
Extech offers repair and calibration services for the products we sell. Extech also
provides NIST certification for most products. Call the Customer Service Department for
information on calibration services available for this product. Extech recommends that
annual calibrations be performed to verify meter performance and accuracy.
Safety
•Use extreme caution when the laser pointer beam is on
•Do not point the beam toward anyone's eye or allow
the beam to strike the eye from a reflective surface
•Do not use the laser near explosive gases or in other
potentially explosive areas

Model 42540A V2.1 January 20063
Meter Description
1. Laser pointer beam
2. IR Sensor
3. Measurement Trigger
4. Battery and Switch Compartment
5. LCD Display
6. Push-buttons
7. Handle Grip
8. Temperature Units (ºC/ºF) Switch
9. Test Lock ON/OFF Switch
10. Alarm ON/OFF Switch
Note: There is a tripod mount on the bottom of the handle
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42540
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Model 42540A V2.1 January 20064
Operating Instructions
Basic IR Measurements
1. Hold the meter by its handle and point it toward the surface to be measured.
2. Pull and hold the trigger to turn the meter on and begin testing. The temperature
reading, the flashing ‘SCAN’ icon, the emissivity, and the unit of measure will appear.
Note: Replace the 9V battery if the display does not switch on.
3. Release the Trigger and the reading will hold for approximately 7 seconds (HOLD will
appear on the LCD) after which the meter will automatically shut off. The only
exception to this is if the TEST LOCK switch is set to ON.
Note: Select the temperature units (ºF/ºC) using the top switch inside the battery
compartment
Backlight/Laser Pointer
1. While pulling the Trigger, push the backlight/laser button once to turn on the
backlight.
2. Press it again to turn on the laser pointer. When the laser is ON the laser icon will
appear in the LCD.
3. Press the laser button to turn the backlight off.
4. Pressing it again turns the laser off.
Note: Backlight and Laser settings will be retained after the meter powers down.
Over-range Indication
If the temperature measurement exceeds the specified temperature range, the
thermometer will display dashes in place of a temperature reading.

Model 42540A V2.1 January 20065
The MODE button options
The MODE button is used to access the programming functions of the instrument. The
selected function is displayed on the bottom line of the LCD. Each parameter is listed
below with an explanation for its use. Press the MODE button to step from one parameter
to the next.
EMS (Emissivity Value)
To change the emissivity value, use the UP and DOWN arrows (the range is 0.10
to 1.00). The current emissivity setting is always shown at the top of the LCD
display. A setting of 0.95 covers about 90% of all applications and, when in doubt,
should be set as such. Emissivity is discussed in a dedicated section of this
manual.
MAX (Maximum function)
In the MAX mode, only the highest reading encountered in the current
measurement session is displayed
MIN (Minimum function)
In the MIN mode, only the lowest reading is displayed
DIF (Max minus Min value)
In the DIF mode, the MAX less the MIN is displayed.
AVG (Average value)
In the AVG mode, all of the readings in the current measurement session are
averaged and the value is displayed.
HAL (High Alarm setting)
The temperature that, when exceeded, causes the audible/visual alarm to trip.
LAL (Low Alarm setting)
The temperature that, when exceeded high to low, causes the audible/visual
alarm to trip.
High and Low Alarm Feature
The Model 42540a has an alarm feature whereas a High Alarm setting and a Low Alarm
setting can be programmed by the user. When either Alarm point is reached the meter will
alert the user via an audible beep and LCD display icon. Follow the steps below:
1. Press the MODE button until the HAL (High Alarm) parameter is displayed. Use the
UP and DOWN arrow keys to set the desired High Alarm temperature setting.
2. Press the MODE button until the LAL (Low Alarm) parameter is displayed. Use the
UP and DOWN arrow keys to set the desired Low Alarm temperature setting.
3. When an alarm limit is reached, the audible alarm will sound and the display icon
HIGH or LOW will appear on the LCD.
4. Note that if the bottom switch (located in the battery compartment) is set to OFF, the
audible alarm will be disabled.

Model 42540A V2.1 January 20066
Battery Replacement
When the battery symbol appears empty or close to empty, replace the
meter’s 9V battery. The battery compartment is located behind the panel
that surrounds the meter’s trigger. The panel can be pried open near the
trigger and folded down as shown in the diagram. Replace the 9V battery
and close the battery compartment cover.
IR Measurement Notes
1. The object under test should be larger than the spot (target) size calculated by the field
of view diagram (printed on the side of the meter and in this guide).
2. Before measuring, be sure to clean surfaces that are covered with frost, oil, grime, etc.
3. If an object's surface is highly reflective, apply masking tape or flat black paint to the
surface before measuring. Allow time for the paint or tape to adjust to the temperature
of the surface it is covering.
4. Measurements through transparent surfaces such as glass may not be accurate.
5. Steam, dust, smoke, etc. can obscure measurements.
6. The meter automatically compensates for deviations in ambient temperature. However,
it can take up to 30 minutes for the meter to adjust to extremely wide changes.
7. To find a hot spot, aim the meter outside the area of interest then scan across (in an up
and down motion) until the hot spot is located.
Field of View
The meter’s field of view is 16:1. For example, if the meter is 16 inches from the target
(spot), the diameter of the target must be at least 1 inch. Other distances are shown in the
field of view diagram. Note that measurements should normally be made as close as
possible to the device under test. The meter can measure from moderate distances but the
measurement may be affected by external sources of light. In addition, the spot size may
be so large that it encompasses surface areas not intended to be measured.

Model 42540A V2.1 January 20067
Emissivity and IR Measurement Theory
IR Thermometers measure the surface temperature of an object. The thermometer’s optics
sense emitted, reflected, and transmitted energy. The thermometer’s electronics translate
the information into a temperature reading which is then displayed on the LCD.
The amount of IR energy emitted by an object is proportional to an object's temperature
and its ability to emit energy. This ability is known as emissivity and is based upon the
material of the object and its surface finish. Emissivity values range from 0.1 for a very
reflective object to 1.00 for a flat black finish. For the Model 42540a, the emissivity is
adjustable from 0.1 to 1.00. Most organic materials and painted or oxidized surfaces have
an emissivity factor of 0.95. When in doubt, set the emissivity to 0.95.
Emissivity Factors for Common Materials
Material under test Emissivity Material under test Emissivity
Asphalt 0.90 to 0.98 Cloth (black) 0.98
Concrete 0.94 Skin (human) 0.98
Cement 0.96 Leather 0.75 to 0.80
Sand 0.90 Charcoal (powder) 0.96
Soil 0.92 to 0.96 Lacquer 0.80 to 0.95
Water 0.92 to 0.96 Lacquer (matt) 0.97
Ice 0.96 to 0.98 Rubber (black) 0.94
Snow 0.83 Plastic 0.85 to 0.95
Glass 0.90 to 0.95 Timber 0.90
Ceramic 0.90 to 0.94 Paper 0.70 to 0.94
Marble 0.94 Chromium Oxides 0.81
Plaster 0.80 to 0.90 Copper Oxides 0.78
Mortar 0.89 to 0.91 Iron Oxides 0.78 to 0.82
Brick 0.93 to 0.96 Textiles 0.90

Model 42540A V2.1 January 20068
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Support line [phone]
Technical support: Extension 200; E-mail: [e-mail]
Repair & Returns: Extension 210; E-mail: [email protected]
Product specifications subject to change without notice
For the latest version of this User’s Guide, Software updates, and other
up-to-the-minute product information, visit our website: www.extech.com
Extech Instruments Corporation, 285 Bear Hill Rd., Waltham, MA 02451
Specifications
Infrared Thermometer Specifications
Range / Resolution -58 to 1400oF (-50 to 760oC) 0.1oC/F over entire range
Accuracy
(of reading) ± 2% of reading or 4oF (2oC) whichever is greater < 932oF (500oC)
± (2.5% of reading + 5o) > 932oF (500oC)
Note: Accuracy is specified for the following ambient temperature
range: 64 to 82°F (18 to 28°C)
Emissivity Adjustable from 0.1 to 1.00 (0.95 default value)
Field of View D/S = Approx. 16:1 ratio (D = distance, S = spot)
Laser power Less than 1mW
Spectral response 6 to 14 µm (wavelength)
General Specifications
Display 4½ digit backlit LCD display with function indicators
Display rate 1 second approx.
Operating
Temperature 32°F to 122°F (0°C to 50°C)
Operating Humidity Max. 80% RH.
Power Supply 9V battery
Automatic Power Off Approx. 6 seconds after the trigger is released
Safety compliance CE
Weight 10.2 oz. / 290g
Dimensions 3.9 x 2.2 x 9.0” (100 x 56 x 230mm)
Copyright ©2006 Extech Instruments Corporation.
All rights reserved including the right of reproduction in whole or in part in any form.