Understanding Infrared Thermography Reading 7 Part 2 of 2.pdf

NETD - Noise Equivalent Temperature Difference
Noise Equivalent Temperature Difference is used to measure the
performance of a infrared cameras ability discern the minimum level of
thermal sensitivity and is very similar to the MRTD with the exception that the
test is based on the output of the detector only, without taking into
consideration the performance of the infrared cameras image as it would be
displayed to a thermographer. The results are usually expressed as the
NETD. A common specification for an IR cameras NETD is 0.02 deg. C at 30
deg. C.
MRTD - Minimum Resolvable Temperature Difference
Minimum Resolvable Temperature Difference is a test developed by the
Department of Defense (ASTM Standard E1213) and used to measure the
performance of a infrared cameras ability discern the minimum level of
thermal sensitivity that a operator of the camera can see. The test involves
selecting the smallest test pattern (4 bars with a 7:1 length to width aspect
ratio) that can be clearly distinguished by the operator as viewed on a display.
Charlie Chong/ Fion Zhang
http://www.prothermographer.com/training/IRBasics/qualitative_thermography/mrtd
_minimum_resolvable_temperature_difference.htm