Pir Manuals

Precision Infrared Radiometer The PIR was a development of the Eppley Precision Spectral Pyranometer, Model PSP and continues to be the industry standard for precise measurement of incoming or outgoing longwave radiation. The PIR comprises the same wirewound thermopile detector and temperature compensation circuitry as found in the PSP. This thermopile detector is used to measure the “net radiation” of the PIR and a case thermistor (YSI 44031) is used to determine the outgoing radiation from the case. A dome thermistor is also included if one wishes to measure the dome temperature as compared to the case temperature to make any “corrections” to the final result. Also included but being discontinued is circuitry for the “Simple Method” of operation. Years ago, when measuring thermistors was fairly difficult for routine users, some researchers opted to use the simple method to measure the solar radiation. A battery – thermistor – shunt resistor circuit was included and created a signal that would approximate the instrument’s outgoing radiation and was measured in series with the thermopile’s net signal. This method was not as precise but more convenient for many people as only one analog signal was measured and a single calibration constant applied. These batteries are no longer manufactured and there is no direct replacement. To shield the thermopile from shortwave radiation, Eppley uses a silicon hemisphere with a vacuum deposited filter on the inside dome. The transmittance of this dome resembles that of silicon with a sharp lower cut-on between 3.5 and 4 microns. Please do not remove the dome for any reason.