Abstract
Least squares fitting is used to fit the function 1/T=polynomial (logR) to data on thermistor resistance, R, versus temperature, T, over the range 0–30°C. For an accuracy of 0·001°C, the polynomial must be of third degree, requiring a minimum of four calibration points. Within a batch of thermistors, the behaviour is sufficiently similar for a reduction in the number of necessary calibration points to be possible if the mean properties of the batch are used to determine the higher order polynomial coefficients. After eliminating one thermistor with high drift from the 21 tested, the mean value of the root mean square drift of ice-point resistance corresponds to a random walk temperature drift not exceeding 0if0·00125°Cyr 1/2. The effect of pressure on the steel probe type of thermistor is 1·3 × 10 −6 ± 1·5 × 10 −6 (standard deviation) °C/bar at pressures up to 700 bar (10,000 psi).
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