Characterisation of dynamic response of thermoresistive sensors

Experimental methods are presented to determine the time constant of a thermoresistive detector to be employed in an electrical equivalence radiometer configuration based on a feedback bridge structure. Electrical circuit configurations for determining the detector resistance variation, in response to Joule heating and incident radiation thermal power input steps, are presented. The time constant of a typical detector is found to be on the order of 15 s, which would normally rule out its use in applications requiring measurement of rapid changes in the incident radiation. However, in the feedback bridge structure the meter response time is reduced owing to the feedback gain of the amplifier. Preliminary experimental determination of the overall response time of the above structure to a sudden change in incident radiation indicates that it is considerably reduced