Development of a functional model of the temperature meter

Abstract

Thin-film platinum resistance thermometers of various designs and performance are widely used in various industries. The temperature measurement range of these sensors is from -200 °C to +600 °C.
 A functional model of a portable digital temperature meter in the range from -50 °C to +300 ℃ based on the L416 sensor type Pt100 is proposed. The optimal circuit solution for connecting the L416 sensor to the Winston measuring bridge was selected. The proposed circuit solution is suitable for power supply from autonomous DC sources, which allows for miniaturization of the device and contributes to energy efficiency.
 The amplification of the output voltage of the amplifier in the entire operating range of the analog-to-digital converter following the operating range of the temperature sensor has been performed, which allows obtaining the maximum resolution of the analog-to-digital conversion when measuring temperature.
 A functional model for converting the resistance of a temperature sensor into a digital code has been developed. The functional model shows that the source code of the analog-to-digital converter does not depend on the supply voltage of the circuit, thus realizing the stability of the function of converting the resistance of the sensor into the value of the code of the analog-to-digital converter.
 The sensor has a normalized characteristic of the dependence of resistance on temperature, so a precision resistance box MSR-60M has been used to calibrate the circuit of the temperature meter. With the help of the resistance box MSR-60M, it is possible to calibrate the circuit of the temperature meter with an uncertainty of 0.07 °C.
 Keywords: temperature meter; RTD; Pt100; Winston bridge; ratiometric power supply.