Design of a thermal converter with frequency output

This paper describes the design for a thermal converter (TC) with frequency output under development at INMETRO. The TC uses commercially available discrete components, eliminating the need for large investments in special environments (clean rooms) for its construction. Today's available surface-mount resistors for high frequency applications display nearly pure resistive behavior up to the GHz region, enabling the operation of the TC in a wide frequency range. A thermistor is used as temperature sensor, connected to an oscillator in order to provide a frequency output proportional to the input power.