Calibration of Non Quadratic Sensibility Thermal Converters

A measurement system for the ac-dc transfer difference of thermal converters whose power response is not exactly quadratic is presented. The previous method, due to the simplifications of the equations, was not valid for those ac-dc transfer standards with a sensibility slightly different from 2. The error in using these equations for those standards has been evaluated and can be as high as 20 μV/V when dealing with single junction thermal converters whose sensibilities can be around 1.6. In the new measurement system, some terms, before considered negligible, have been retained. A modified bridge has been developed according to this equation to allow the calibration of all kind of thermal converters, including those with sensibilities not exactly quadratic. This new bridge has been validated with some measurements as detailed below in this paper.