In the broadest sense, a photometer is any instrument used to measure illuminance or irradiance. As applied in industrial photometry, a "photometer" is the general term covering instruments for detecting:

• scattered light intensity
• absorption
• fluorescence

Most photometers are based on a photoresistor or photodiode. Either exhibits a change in electrical properties when exposed to light, which can be detected with a suitable electronic circuit.

See also

• Photodetector A transducer capable of accepting an optical signal and producing an electrical signal containing the same information as in the optical signal. The two main types of semiconductor photodetectors are the photodiode (PD) and the avalanche photodiode (APD).

Measuring instruments | Optical devices

Luxmetr | Fotometer | Fotómetro | Lichtmeter | Fotômetro | Фотометр | Fotometer