Construction of a calorimeter prototype with a high sensitivity pulsed signal detection circuit.

A calorimeter based on a Wheatstone bridge detector is considered to be an ideal absolute absorbed dose measuring device. One drawback of the calorimeter is that its output signals are extremely small. The signal size can be increased by increasing the bridge excitation voltage, which, however, may lead to excess self-heating of a temperature-sensing thermistor in the calorimeter detector and may require corrections. The use of pulsed excitation was investigated in this study in place of a conventional DC excitation to induce higher bridge output voltage while keeping the average self-heating of a thermistor to a reasonably low value. Performance evaluations of our prototype pulsed calorimeter are presented.