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Glossary of Thermography Terms

Noise Equivalent Temperature (difference), NET (D)

The temperature difference that is just equal to the rms noise signal; a measure of thermal resolution; (thermal sensitivity), but not talking into account target size, characteristics of the display and the subjective interpretation of the operator.

NIST, NIST Traceability

The national Institute of Standards and Technology (formerly NBS). Traceability to NIST is a means of ensuring that reference standards remain valid and their calibration remains current.


An object whose emissivity varies with wavelength over the wavelength interval of interest. A radiating object that dose not have a spectral radiation distribution similar to a blackbody and can be partly transparent to infrared (transmits infrared energy at certain wavelength); also called a “colored body “or “real body “. Glass and plastic films are examples of non–graybodies. An object can be a graybody over one wavelength interval and a non–graybody over another.

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