DR VAKU ® Infrared Digital Temperature Gun, Resolution Infrared Thermometer, Multi-Purpose, Wide Range, Non-Contact [With Free Battery]How To Measure Take it 10 cm away from the forehead person. Click the start button, reading complete after a short beep. Note down the temperature. Note: Remember that when you use a digital thermometer to check your temperature, the reading from your armpit (axillary) will be about half to one degree Fahrenheit (0. 6 degrees Celsius) lower than if you took the temperature orally (by mouth). Rapid Temperature Measurement: Measure Body Temperature