Extech Instruments 42511 User manual

User’s Manual
Dual Laser InfraRed (IR) Thermometer
MODEL 42511

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Introduction
Congratulations on your purchase of the Model 42511 IR Thermometer. This Infrared
thermometer measures and displays non-contact temperature readings up to 1100oF
(600oC). At 12”, the built-in dual lasers converge to 1” target spot to insure accurate
targeting and temperature measurement. The adjustable emissivity feature allows the IR
thermometer to measure the temperature of virtually any surface. Proper use and care of
this meter will provide years of reliable service.
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and
workmanship for three 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.
Safety
•Use extreme caution when the laser pointer 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

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Meter Description
1. Dual Laser pointers
2. LCD Display
3. Function Buttons
4. Measurement Trigger
5. Battery and F/C Switch compartment
DISPLAY
1. SCAN, measurement in progress
2. HOLD, last measurement locked in display
3. Laser pointer active
4. Power locked ON
5. High limit alarm
6. Low limit alarm
7. C or F temperature units
8. Main temperature display
9. Low battery icon
10. MAX icon
11. Emissivity setting
12. Emissivity icon
13. Max temperature display

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Operating Instructions
Temperature 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, MAX temperature reading, the ‘SCAN’ icon, the emissivity value, and the unit
of measure will appear.
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 is if the LOCK mode is set to ON.
Note: Select the temperature units (ºF/ºC) using the switch inside the battery
compartment
Field of View
The meter’s field of view is 12:1. For example, if the meter is 12” (30cm) from the target
(spot), the diameter of the target must greater than 1” (2.5cm). Other distances are shown
in the field of view diagram (illustrated below and on the side of the meter). Measurements
should normally be made as close to 12” as possible to the device under test. The meter
can measure from greater 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.
Dual Laser Pointer
The dual laser pointers are designed to cross at a
distance of 12” (30cm). The spot size at this distance is
1” (2.5cm) in diameter and this is the recommended
distance to target for most measurements. To turn the
lasers on/off:
1. Press and release the Trigger
2. While HOLD is on the display, press the laser button
once to turn on the lasers on or off.
3. The laser icon will appear in the LCD when the
laser function is enabled.
4. The status of the laser will be stored in memory and
will remain as the ON condition until changed.
@12”
1”
@18”
1.5”
@30cm
2.5cm
@45cm
3.75cm
@6”
0.5”
@150mm
12.5mm

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MAX (maximum) temperature display
The highest reading encountered during a single measurement scan is displayed in the
MAX display field.
Backlight
1. Press and release the trigger
2. While HOLD is on the display, press the backlight button once to turn on the
backlight on or off.
3. The backlight will illuminate in the LCD when the feature is enabled.
4. The status of the backlight will be stored in memory and will remain as the ON
condition until changed.
5. Note: Use this feature sparingly and only as needed since the backlight puts an extra
strain on the battery.
The MODE button options
The MODE button is used to access the Test Lock, High alarm, Low alarm and Emissivity
adjustment features of the instrument.
1. Press and release the trigger
2. While HOLD is on the display, press the MODE button to step through and program the
following features. A blinking icon indicates the feature is selected.
E= (Emissivity Value)
Press the ▲or ▼button to change the emissivity value
(Test Lock mode On/Off)
Press the ▲or ▼button to turn the lock feature ON or OFF
(High Alarm On/Off)
Press the ▲or ▼button to turn the High Alarm feature ON or OFF
(High Alarm setting)
Press the ▲or ▼button to set the high alarm limit value in the main display
(Low Alarm On/Off)
Press the ▲or ▼button to turn the High Alarm feature ON or OFF
(Low Alarm setting)
Press the ▲or ▼button to set the Low alarm limit value in the main display

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Emissivity Adjust
The adjustable emissivity feature allows the user to measure many surface colors, finishes,
and textures. A separate section is provided later in this guide that covers emissivity in
greater detail.
Test Lock feature
The Test Lock feature disables the Auto Power Off feature for the period of use when
selected. The feature is useful for long term temperature monitoring and hands free use.
The meter will revert to auto power off if the trigger is pressed during a locked scan.
High and Low Alarm Feature
The meter has a programmable high and low alarm feature. When either alarm point is
reached the meter will alert the user via an audible beep and a blinking LCD display icon.
The alarm limit is set and the feature is enabled/disabled using the MODE button. The
setting is stored and memory and will remain as the “turn-on” condition until changed.
Temperature Units
The temperature units can be set to °F or °C using the switch located in the battery
compartment.
Over-range Indication
If the temperature measurement exceeds the specified temperature range, the
thermometer will display dashes in place of a temperature reading.
Battery Replacement
When the low battery symbol appears on the display, replace the
meter’s battery (9V). The battery compartment is located behind the
panel that surrounds the meter’s trigger. Open the compartment by
pulling the panel down from the trigger area. Replace the 9V battery
and close the battery compartment cover.

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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 or side to side motion) until the hot spot is located.
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 42511, 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

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Specifications
Range -58 to 1100oF (-50 to 600oC)
Resolution 0.1o< 1000 o,1o> 1000 o
Accuracy -58°F to 28°F (-50°C to -2°C) ±9°F/4°C
28°F to 200°F (-2°C to 94°C) ±4.5°F/2.5°C
200°F to 400°F (94°C to 204°C) ±(1.0%rdg + 2°F/1°C)
400°F to 800°F (204°C to 426°C) ±(1.5%rdg + 2°F/1°C)
800°F to 1100°F (426°C to 600°C) ±(4%rdg +2°F/1°C)
Note: Accuracy is specified for the following ambient temperature
range: 73 to 77°F (23 to 25°C)
Emissivity 0.10 to 1.00 adjustable
Field of View D/S = Approx. 12:1 ratio (D = distance; S = spot or target)
Laser pointer Dual, Class 2 laser < 1mW power; Wavelength is 630 to 670nm
IR Spectral response 8 to 14 µm (wavelength)
Repeatability ± 0.5% of reading or ± 1.8oF (1oC) whichever is greater
General Specifications
Display Backlit LCD display with function indicators
Response time 150ms
Over range indication “---------“
Operating Temperature 32oF to 122oF (0oC to 50oC)
Operating Humidity 10% to 90%RH operating, <80%RH storage.
Storage Temperature 14 to 140oF (-10 to 60oC)
Power Supply 9V battery
Automatic Power Off 7 seconds, with LOCK to disable
Weight 5.7 oz. (163g)
Dimensions 5.7 x 4 x 1.6” (146 x 104 x 43mm)