Extech 42500 Thermometer


Extech 42500 Thermometer This thermometer makes 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.



  • Built-in laser pointer identifies target area
  • Backlighting illuminates display for taking measurements at night or in areas with low background light levels
  • Automatic Data Hold when trigger released
  • Fixed 0.95 emissivity covers 90% of surface applications
  • Auto power off

Mini IR Thermometer Details

Smaller than your typical infrared thermometer, the Extech 42500 Mini IR Thermometer allows you to get a thermal reading without coming into contact with the object you are analysing, and offers a distance to target ratio of 6:1. Although Extech has not offered a feature which allows you to adjust the emissivity settings of this infrared thermometer, research from the manufacturer shows that the device’s optimal accuracy can be achieved on more than 90% of surfaces. As standard, this level is set at 0.95.

Moving on to the other useful features of the Extech 42500 Mini IR Thermometer, and the display ensures that you will be able to use this infrared thermometer in even the most trying conditions. Whether you are working in the dark or in a dimly-lit environment, all you need to do is activate the backlight, and the laser will also help you to accurately decide which areas need a reading.

One typical question that Extech get asked is how the laser ratio on the Extech 42500 Mini IR Thermometer works. Because of this, an explanatory diagram can be found on the side of this infrared thermometer. Basically, if you are 30 inches away from the surface you are targeting, this means that the target should be six times less than your distance. You will know that this has been achieved when the diameter of the laser pointer is five inches.

The Extech 42500 Mini IR Thermometer weighs just 140g, so it really is a mini infrared thermometer! This Extech device can provide a thermometer temperature that ranges from -20 to 260 degrees Celsius, or -4 to 500 degrees Fahrenheit. You can change how the parameter is measured by using the simplistic buttons found just underneath the display.


Thermometers/IR Thermometers Template

IR Temperature Max 500 F
IR Temperature Min -4 F
Field View Ratio (Spot Ratio) What's This? 6:1
Accuracy ± 2% of reading or ±2°C (4°F) whichever is greater, from 15 to 50°C (60 to 113°F)
± 3% of reading or ±3°C (6°F) whichever is greater, for remainder of range: -20 to 260°C (-4 to 500°F)

Note: Accuracy is specified for the following ambient
temperature range: 18 to 28°C (64 to 82°F)
Laser Pointer What's This? Yes
Backlight Yes
Emissivity Adjustable What's This? No
Alarm No
Data Hold What's This? Yes
Max./Min. What's This? No
Memory Recall What's This? No
Thermocouple Input What's This? No
Food Safe What's This? No


Infrared Thermometer Specifications
Range / Resolution -4 to 500°F (-20 to 260°C), 1°C/F
Accuracy ± 3% of reading or ± 6°F (3°C) whichever is greater.
Note Accuracy is specified for the following ambient temperature range: 64 to 82°F (18 to 28°C)
Emissivity 0.95 fixed value
Field of View D/S = Approx. 6:1 ratio (D = distance, S = spot)
Laser power Less than 1mW
Spectral response 6 to 14 µm (wavelength)
General Specifications
Display 2000 count, 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 Meter shuts off automatically after 6 seconds
Weight 4.9 oz. / 140g
Dimensions 6.7 x 1.7 x 1.6” (170 x 44 x 40mm)


Product Images (click to enlarge)
  • Extech 42500 Thermometer