Noise Equivalent Temperature Difference

If you are buying an infrared camera, or anything really, you want to know about specifications so that you can compare different products objectively and find the one that is best for you. If so, you are going to come across the noise equivalent temperature difference (NETD). It is also generally referred to as thermal contrast and usually expressed in milli-Kelvin (mK).

Thermal contrast is a primary specification of infrared cameras that determine their suitable uses. It describes how well the thermal imaging sensor is able to distinguish the differences in thermal radiation in an image. The smaller the value of the thermal contrast, the more accurate the instrument. An infrared camera with 120mK would produce more accurate images compared to another camera with 150mK NETD.

Another effect of smaller NETD is better image quality. A smaller value means smoother transition between different temperatures which produces less noise in the image. A difference of 30mK in NETD makes a significant difference in image quality.

The NETD can be affected by several factors. Some infrared cameras come with multiple calibrated temperature measurement range. The amount of noise in the image can vary depending on the range chosen and the temperature of the object. What is important to keep in mind is that as long as the image has significant thermal contrast and the temperature of the object is significantly higher than the background, the accuracy of the measurement should not be affected.