Szybka korekcja statycznych charakterystyk termometrycznych termistorów

W artykule przedstawiono metodę szybkiej korekcji statycznych charakterystyk termometrycznych termistorów. Zastosowano komputerowy system pomiarowy z wzorcowym czujnikiem platynowym oraz elementem wykonawczym w postaci pompy ciepła Peltiera. Zaprezentowano wyniki pomiarów. Przestawiono metodę wyznaczania zmodyfikowanych parametrów charakterystyki termometrycznej na podstawie przeprowadzonych pomiarów.

The paper presents a method for fast correction of static characteristics of NTC thermistors and a measurement-control system with dedicated software. The measurement system uses a high performance current source and ADC card with 16-bit converter and a USB interface. The control unit uses a three-stage Peltier heat pump that enables fast and simple stabilization of the temperature in the range (20 ÷ 85) °C. Using a software PID controller and a standard Pt100 temperature sensor the stability achieved was at the level of š 0.02°C over the full range. Corrections were carried out by classifying sensors to one of three categories (I, II, III) and then a specific set of coefficients was assigned for the static characteristics. The paper presents the detailed algorithm for the procedure including the method for determining the adjusted static characteristic coefficients. The coefficients were determined by the optimal value search method minimising along orthogonal directions. Approximately 20% of the test sample that contained 35 pcs sensors did not require correction. The accuracy of other sensors was improved three times at least by the correction applied.