Pyroelectric null detector for absolute radiometry.

A pyroelectric detector has been so designed that the sensing element is comprised of two uniformly poled crystal plates joined together so that the polarity of the domains reverses across the junction. The front electrode of the detector is used for absorption of radiation and the back electrode for producing electric heating pulses. An in-phase signal taken by a photodiode is used to produce electric heating pulses in the detector through a heater amplifier. A null output is obtained when radiation power is equal to electric heating power. The pyroelectric null detector (PND) has been used for absolute measurement of radiation.