Introduction to pt100 temperature sensor

PT100 is a Temperature sensor. It is a platinum wire thermal resistance sensor with good stability and linearity. It can work in the range of -200 °C to 650 °C.

Resistive Temperature Detector (RTD) is a kind of resistance made of material material. It changes the resistance value as the temperature rises. If it rises with the temperature, the resistance value also rises, which is called positive resistivity. If it rises with the temperature and the resistance value decreases, it is called the negative resistivity. Most resistive temperature detectors are made of metal. Among them, resistive temperature detectors made of platinum (Pt) are the most stable - acid and alkali resistant, non-deteriorating, fairly linear... most used by industry.

The PT100 temperature sensor is a resistive temperature detector made of platinum (Pt), which belongs to the positive resistivity. The relationship between resistance and temperature change is as follows: R = Ro(1 + αT) where α = 0.00392, Ro It is a 100 Ω (resistance value at 0 ° C), T is a temperature range of Celsius, so platinum is a resistive temperature detector, also known as PT100.

1: Vo = 2.55 mA × 100 (1 + 0.00392 T) = 0.255 + T / 1000.

2: When measuring Vo, no current can be separated, otherwise the measured value will be inaccurate. Circuit analysis Because the power supply is more than the general power supply, the power supply is with noise, so we use Zener diode as the voltage regulator part, because of the role of 7.2V Zener diode, make 1K resistor and 5K variable resistor The voltage sum is 6.5V, and the adjustment of the 5K variable resistor determines the emitter (collector) current of the transistor. We must adjust the collector current to 2.55mA, so that the measurement voltage V is 0.255 as indicated by the arrow. +T/1000. Subsequent non-inverting amplifiers, the input resistance is almost infinite, and at the same time amplified 10 times, making the op amp output 2.55 + T / 100. 6V Zener diode role as 7.2V Zener diode, We use it to call up 2.55V, so the output voltage V1 of the voltage follower is also 2.55V. The output of the differential amplifier is then Vo=10(V2-V1)=10(2.55+T/100-2.55)=T/10. If the room temperature is now 25°C, the output voltage is 2.5V.