Also called brightness pyrometer it uses a narrow band of radiation within the visible range (0.4 to 0.7 microns) to measure temperature by color matching and other techniques.
A device for measuring the temperature of an incandescent radiating body by comparing its brightness for a selected wavelength interval within the visible spectrum with that of a standard source; a monochromatic radiation pyrometer. Temperatures measured by optical pyrometers are known as brightness temperatures and except for black bodies are less than the true temperatures.
A system that, by comparing a source whose temperature is to be measured to a standardized source of illumination (usually compared to the human eye), determines the temperature of the former source.
A temperature measuring device through which the observer sights the heated object and compares its incandescence with that of an electrically heated filament whose brightness can be regulated; or the intensity of the light admitted from the object may be varied through filters and compared with a constant light source. See Pyrometer.