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Short-Term Stability Measurements of a Germanium Plotodiode Radiometer



G Andor, Bettye C. Johnson


This paper describes a general stability measurement method for the short term stability, or repeatability, for radiometers using fixed-point blackbodies [BBs] as radiation sources. A germanium photodiode was used for the detector in the radiometer. The radiance during the melts and freezes was measured five times for a total of 14 h to 18 h with the radiometer for each BB. The undercooling of the freeze was used as a reference signal to establish a common temporal scale for the five data sets. The average of the standard deviations of the five measurements at each time t determined the standard uncertainty. This uncertainty includes the instability of the radiometer and the BB radiance as a function of time. Four BBs were measured with the radiometer. The repeatability of the output signal was found to be 0.006% to 0.002% in the optical power range from about 2 nW to 2mW. The repeatability determined using this method represents an upper limit of the short-term repeatability of the germanium radiometer.


blackbody sources, germanium photodiode, optical radiation, radiometer repeatability, stability


Andor, G. and Johnson, B. (1998), Short-Term Stability Measurements of a Germanium Plotodiode Radiometer, Metrologia (Accessed April 18, 2024)
Created October 1, 1998, Updated February 17, 2017