Platinum resistance temperature sensor wiring principle

Two -line system
The changing value of the sensor resistance and the connection wire resistance value together constitute the output value of the sensor. Due to the additional error caused by the wire resistance, the actual measurement value is high, and it is used to measure the accuracy of the accuracy, and the length of the wire should not be too long.


Three -line system
The cross -sectional area and length of the three wires required are the same. The circuit that measures the platinum resistance is generally unbalanced bridge. Platinum resistance is used as a bridge arm resistance as a bridge. Receive the bridge arm where the platinum resistance is located and the adjacent bridge arm. When the bridge is balanced, it can be seen that the RT = R1R3/R2+R1R/R2-R, when the R1 = R2, the change of the wire resistor changes There is no effect on the measurement results, so that the measurement error caused by the wire resistance of the wire line is eliminated, but it must be a bridge of the whole class. Otherwise, it is impossible to completely eliminate the effect of the wire resistance. The additional errors brought by the wire resistance, the three -line connection method is generally adopted in the industry.
Four -line system
When the measurement resistance value is very small, the resistance of the test line may introduce significant errors. Two additional test cables are used to provide constant current with two additional test lines. Below, the current does not flow through the voltage meter, so that the voltage drop on the unknown resistance can be accurately measured, and the resistance value can be calculated by calculating.