Platinum resistance high-precision temperature measurement system

Temperature is a very important measurement parameter in industrial production processes, and the accuracy of temperature measurement and control directly affects product production and quality. With the development of measurement technology, the demand for temperature measurement accuracy is also increasing. For example, in the joint production of alkali in the chemical industry, the temperature difference is required to be controlled at 0.2 ℃. Within the working range of the chromatograph, temperature measurement is required to be better than 0.05 ℃. Platinum resistance temperature sensors are widely used as ideal temperature measuring elements in industrial precision measurement systems due to their high accuracy, good linearity, fast response speed, and many other advantages. The use of platinum resistors for high-precision temperature measurement requires overcoming several technical difficulties, such as lead resistance, self heating effect component drift, and noise interference.
The high-precision temperature measurement scheme using platinum resistance as the temperature measuring element solves some basic requirements for hardware circuits in platinum resistance temperature measurement, but the measurement accuracy is poor; Fang Yixi et al. [3] designed a high-precision temperature measurement system driven by a constant current source for three wire platinum resistors, which provides a good calibration method for measurement errors and temperature drift, but does not effectively solve the impact of lead resistance on temperature measurement; Wang Guoding et al. [4] proposed a constant current source driven four wire platinum resistance measurement method, which effectively solves the lead resistance and self heating effect of platinum resistance. However, they did not analyze in detail the impact of external interference on system measurement in practical applications, nor did they provide corresponding suppression measures.
The temperature measurement scheme using micro current driven four wire platinum resistance Pt100 can completely eliminate the error caused by lead resistance, effectively reduce self heating effect, and improve the measurement accuracy and stability of the system by using software and hardware anti-interference filtering technology to reduce noise, suppress interference, and reduce system errors.
1 Platinum resistance high-precision temperature measurement system
Platinum resistance Pt100 is a temperature sensor made by utilizing the physical properties of the resistance value of platinum (Pt) metal, which changes with temperature. The key to using Pt100 as a temperature measuring element for temperature measurement is to accurately measure the resistance value of Pt100.
According to the temperature characteristics of Pt100, the four wire platinum resistance Pt100 high-precision temperature measurement system is shown in Figure 1. The system mainly consists of a constant current source driving circuit, a four wire platinum resistance interface circuit, and an instrument amplifier The circuit consists of an anti aliasing filter circuit, a sample and hold circuit, and an A/D sampling circuit. When the system is measuring temperature normally, a constant current is passed through Pt100 to generate a corresponding voltage signal. The instrument first uses an amplifier circuit to remove common mode interference and amplify it appropriately. Then, high-frequency harmonics are removed through an anti aliasing filter circuit and a sample and hold circuit, and input into a high-precision A/D converter. The digital signal after A/D conversion is fed into the microcontroller system for digital filtering, and finally the true temperature is calculated through a formula.