Development of improved electrical-substitution radiometers at the National Research Council of Canada

We describe the development of a third generation of electrical-substitution radiometers (ESR's) at the National Research Council of Canada. The new ESR's follow the same general design as before, but incorporate improved thermopiles and electrical heating elements. The ESR's have a responsivity between 0.6 and 1.0 VW(-1), a time constant of approximately 2.0 s, a uniformity of 0.1% over a 6-mm-diameter region, and a noise level of approximately 6 nW. Performance characteristics of the new ESR's are discussed. It is shown that calibrations performed with these ESR's agree with those made with the previous generation of ESR's to better than 0.05%.