The spectral response of radiation thermopiles

The spectral response curves of some typical radiation thermopiles, of both vacuum and air types, have been determined by comparison with a specially made nonselective thermopile. The results, which cover the wavelength range 0.6-17.0 μm, are shown graphically. They illustrate that substantial degrees of selectivity may be encountered in practice. The work is also of interest because it revealed sources of error, in the use of radiation thermopiles, which may sometimes pass unrecognized. An appendix describes the specially made thermopile and its properties.