Thermoresistive radiation sensor response time employing electrical heating

The thermal time constant (τ) of a thermoresistive sensor is defined in terms of its physical properties such as mass (m), specific heat (C), area (A), and overall heat transfer coefficient (U) to the surroundings. Measurement of c and U by direct calorimetric methods may involve lengthy experimental procedures. The time constant determination using electrical heating introduces measurement error. An analytical formulation to demonstrate the origin of this error and a procedure to eliminate the same and determination of the values of τ, UA, and mc, are presented. Sensitivity considerations for the choice of appropriate sensor heating currents to minimize some of the measurement errors are also discussed