Why does the PT100 temperature sensor have 3 wires?

1. PT100 temperature sensor usually has 3 lines. Simply put, it is a resistor that changes with temperature.
2. It is called the PT100 temperature sensor because at 0 ° C, it can measure 100 ohms.
3. It is about 138 ohms in the environment.
4. Because each temperature resistance will change very small, when connected to the temperature controller, the additional resistance of the wire will cause errors.
5. In order to eliminate the impact of the wires, we need at least 3 wires.
6. The controller measures the wire resistor and subtracts it, leaving only the PT100 temperature sensor resistance.
7. Under our sketch, we have the following resistors, RPT, R1, R2, and R3
8. Mathematically, the controller does the following calculations ...
9. RPT = "Measure between A and B" is less than "resistance between B and C measurement"
10. So RPT = (R1 + RPT + R2) - (R2 + R3)
11. So the connection position of each wire is important.
12. Under normal circumstances, these wires will be colored, so the two wires are the same color, and the third is different.
13. Wire A can be red, wire B and wire C can be another color, such as black
14. Although it is not very good, electrician often extends the PT100 wire and traditional copper wires. This is good, but it does not conform to the two colors of one color and the other color.
15. If you want to determine which wire starts, and then measures the resistance, between all 3 wires, and use measurement to identify the wires.
16. The measurement value between wire A and wire B will exceed 100 ohms.
17. The measurement values between wire A and wire C are the same.
18. The measurement value between wire B and wire C is very low, only the resistance of the wire itself.
19. Now you have determined which line you are. Now connect them with appropriately, the terminal on the controller.
20. So the mark on the controller is usually B, B, a
21. So these two colors are on B on B on A