PT100 temperature measurement circuit

The pt100 temperature sensor is an instrument that converts temperature variables into a transmittable standardized output signal. Mainly used for measurement and control of temperature parameters in industrial processes. A transmitter with a sensor usually consists of two parts: the sensor and the signal converter. The sensor is mainly a thermocouple or a thermal resistor; the signal converter is mainly composed of a measuring unit, a signal processing and a conversion unit (since industrial thermal resistors and thermocouple scales are standardized, signal converters are also called Transmitter) PT100 temperature measurement circuit, bridge + LM358 operational amplifier measurement signal. Contains multism14 simulation file~~~~ Connect to the two-wire PT100. The bridge voltage is amplified ten times through LM358 (the resistance can be modified by yourself) and amplified for output. The OUT port can read the voltage from the AD port of the microcontroller. The resistance of PT100 can be calculated according to the circuit, and the temperature can be determined according to the look-up table method and the dichotomy method. The temperature can also be calculated according to the formula method, but the result will have errors. ~~~~

Sensor input voltage: 5V Theoretical measurement temperature range: 0-300 degrees Celsius~~~~

Extended information: Its working principle: When the PT100 is at 0 degrees Celsius, its resistance is 100 ohms, and its resistance will increase at an approximately constant rate as the temperature rises. But the relationship between them is not a simple proportional relationship, but should be closer to a parabola. The calculation formula for how the resistance of a platinum resistor changes with temperature: -200<t<0℃ Rt=R0[1+At+Bt*t+C(t-100)t*t*t] 0≤t< 850℃ Rt=R0 (1+At+Bt2) Rt is the resistance value at t℃, R0 is the resistance value at 0℃. A, B, and coefficients in the formula are experimentally determined. Here are the standard DIN IEC751 coefficients: A=3.9083E-3, B=-5.775E-7, C=-4.183E-12. According to the Vedic formula, the conversion of Rt ->t for resistances greater than or equal to 100 ohms is obtained. Formula: 0≤t<850℃ t=(sqrt((A*R0)^2-4*B*R0*(R0-Rt))-A*R0)/2/B/R0