Abstract
The 'Dynamic Thermometer' is a versatile instrument used in conjunction with a platinum resistance sensor which is both accurate and fast. It can measure resistance ratio to an accuracy of 30 ppm or better in less than 1 s. The resolution is programmable in the range 15 bits in 0.6 s or 20 bits in 11 s. In the high-accuracy mode, the readings are converted into temperature measurements according to the ITS-90 scale. In the diagnostic mode, the instrument measures the response to a self-heating step function and determines the thermal parameters of the sensor and its housing without removing it from its working position. This information is useful to check the integrity of the sensor and to estimate its response time. In the high-speed mode, temperature is computed from resistance measurements according to the Callendar equation and digitally compensated so that the overall response time is less than the response time of the sensor alone. Examples of measurements made with the instrument are quoted to illustrate its applications.
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