optris PI 400 LW, Operator'S Manual

Page: 49 / 52

optris PI LightWeight Kit
– E2013-04-B
47
Basics of Infrared Thermometry
Depending on the temperature each object emits a certain
amount of infrared radiation. A change in the temperature
of the object is accompanied by a change in the intensity
of the radiation.
Searching for new optical material William Herschel by
chance found the infrared radiation in 1800.
He blackened the peak of a sensitive mercury thermometer.
This thermometer, a glass prism that led sun rays onto
a table made his measuring arrangement.
With this, he tested the heating of different colors of the William Herschel (1738 - 1822)
spectrum. Slowly moving the peak of the blackened
thermometer through the colors of the spectrum, he noticed
the increasing temperature from violet to red.
The temperature rose even
more in the area behind the red end of the spectrum. Finally
he found the maximum temperature far behind the red area.
Nowadays this area is called “infrared wavelength area”.