An Improved Theory of the Instrumental Corrections for Absolute Radiometers

Abstract

An improved theory of the instrumental corrections applied to absolute radiometers, with the exception of the effect of sensitivity variations across the receiver surface, is derived. After a brief review of the historical emergence of correction factors and finally of a formal correction theory, as formulated by Geist [ 131, some shortcomings of t h s theory are pointed out. Based on a set of strict definitions and the conservation of energy principle a revised theory is derived and a possible experimental procedure for the determination of the various correction factors is described. The new theory also takes into account the influence of deviations from linear response, which to a certain extent are present in all practical absolute radiometers. The ratio of the mean sensitivities for radiant and electrical heating is expressed in terms of either the equivalent or non-equivalent lieat losses. By analyzing the one-dimensional heat flow through a representative model of an absolute radiometer the equivalent and non-equivalent losses are identified. At the same time a formal proof for the conception of the equivalence of the heat loss through the heater wires is provided. All correction terms in the new theory are treated as functions of the applied power and can also be determined as such. In conclusion both the scope and the limitations of the theory are discussed.

Spectroradiometric determination of the freezing temperature of gold

“…Due to residual differences in the electrical and radiant heating of an ECR, the temperature rise produced by radiant power is not exactly the same as that produced by an equal amount of electrical power. This non-equivalence of electrical and radiant heating has been examined in detail by Hengstberger [ 29 ]. The determination of the small correction for this non-equivalence is generally a one-time characterization of the ECR, as contrasted with the routine calibration by electrical substitution heating to achieve a thermocouple signal which matches that of an unknown radiant input power.…”

The Absolute Measurement of Radiant Power

“…A detailed study was undertaken of various experimental variants for measuring the lead-heating correction using a Gillham-type lead configuration (Hengstberger, 1977b), and an improved theory of the instrumental corrections for absolute radi ometers was derived (Hengstberger, 1977c). Following the Australian prece dent, the South African photometric scale was officially placed on a radiometric basis during 1976 using a preliminary value of the constant K m of 682.5 lmW -1 .…”

Experimental characterization and correction of non-equivalence of Solar Irradiance Absolute Radiometer

“…OCIS codes: 120.3930, 120.3940, 120.5630. doi: 10.3788/COL201412.101202. the solar radiant power can be determined by calculating the equivalent electrical power. The precondition of the measurement procedure is that the electrical and radiative heating sensitivities of the cavity are equivalent, whereas the difference of these two sensitivities is affirmed, which is entitled non-equivalence [8][9][10] . The non-equivalence is due to the differences in the heating power distribution and thermal diffusion in the cavity during the shaded electrical heating and irradiated radiative heating sequences.…”