Photometer
From ExoDictionary
Photometer
An instrument for measuring the intensity of light or the relative intensity of a pair of lights. Also called illuminometer.
If the instrument is designed to measure the intensity of light as a function of wavelength, it is called a spectrophotometer. Photometers may be divided into two classes: photoelectric photometers in which a photoelectric cell is used to compare electrically the intensity of an unknown light with that of a standard light, and visual photometers in which the human eye is the sensor.
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
