Thermopile With Dvm
To observe infrared radiation.
Thermopile, DVM with TV camera and monitor, heat sources.
The output from a commercial thermopile is connected to a digital voltmeter where the voltage is proportional to the temperature observed: the hotter the object the higher the voltage. Use various sources: ice, boiling water, liquid nitrogen, the floor, people, etc. This is only qualitative; the system is not calibrated.