What is PT100 (RTD)-- Principle and application of 2-wire, 3-wire, and 4-wire
RTDs - or Resistance Temperature Detectors - are temperature type sensors that contain a resistor that can vary with temperature. It has been used in industrial processes and laboratories for many years with precise, reliable, and stable characteristics.
The 2-wire system is the simplest design in RTD. This is a series connection design, with one lead wire at each end of the RTD, which connects to the monitoring equipment. When calculating temperature changes, it is actually calculating the change in resistance value, but this resistance value includes two leads that are resistors and the actual working RTD device, so the results may have some deviation or error.
3-wire PT100
This is something that many people don't understand, and it was also something I didn't quite understand at the time. The 3-wire RTD is the most commonly used in industrial production and monitoring equipment. This configuration has two leads at one end of the RTD and only one lead at the other end.
In this design, you must ensure that the three reference wires R1, R2, and R3 are made of the same material, with consistent length and thickness. This actually means that the resistance values of the three wires are the same.
3-wire PT100
Actually, a subtraction was made in the monitoring device: Rt1=R1+R2+Re
Rt2=R2+R3
Because all three wires are the same: R1=R2=R3
Finally, in the monitoring device, Rt=Rt1-Rt2=Re was obtained
The resistance value measured in this way is the resistance value of Re change, which is already very accurate and not expensive. It is very practical in the industrial field.
