Improvement of Algorithms for Measuring Temperature with Two-Wire Connection of Resistance Thermometers

The existing methods for reducing the error in measuring the temperature of objects and media by resistance thermometers are examined. These errors arise from the influence of the resistance of the connecting lines. It is shown that the methods used in industry for reducing this influence and the corresponding errors are based on three- and four-wire circuits for connecting resistance thermometers, which makes the measurement circuits more complicated and increases the cost of the connecting lines. A two-wire connection scheme is described which can significantly reduce the influence of a connecting line on the accuracy of a temperature measurement. This circuit is distinguished by a simple design and lower cost than three- and four-wire connection schemes. To reduce the sensitivity to interference and quantization noise with a simultaneous reduction in the measurement time, it is proposed that a digital voltage integrator for the transient discharge process of the capacitor shunting the resistance thermometer be installed in the two-wire circuit. A method for two-wire measurement of temperature by resistance thermometers has been implemented in practice using a measurement algorithm developed here along with processing of the results of the digital integration of the transient voltage. Numerous measurements of a standard resistance with a nominal value of 1 kΩ have been made with two-wire temperature measurement employing digital integration and a method with an estimate of the voltage drop at the resistance thermometer based on measurements at two points on the transient curve. Experimental studies have confirmed the effectiveness of the two-wire temperature measurement technique using digital integration. This method can be used in systems for monitoring the parameters of the air environment and of technological processes.