The three wiring methods of platinum resistors are two-wire system, three-wire system and four-wire system.
>Two-wire system>
>Platinum resistor with two-wire system connection method. The output resistance is the resistance value of platinum resistor. Due to the additional error caused by the resistance of the wire, the actual measurement value is higher than the sum of the resistance value of the connecting wire. Therefore, the two-wire processing method is suitable for occasions where the measurement accuracy is not high, and the length of the wire should not be too long. >
>Three-wire system>
>Platinum resistors using the three-wire processing method require that the three lead wires have the same cross-sectional area and length. The circuit for measuring platinum resistance generally uses an unbalanced bridge, and the platinum resistor is used as For an arm resistor of the bridge, connect one wire to the power end of the bridge, and the other two wires to the bridge arm where the platinum resistor is located and the adjacent bridge arm. If the bridge circuit is balanced, through calculation It can be known that changes in wire resistance will not have any impact on the measurement results, thus eliminating the measurement error caused by the resistance on the wire line during measurement. A congruent arm bridge can completely eliminate the influence of wire resistance. However, the analysis shows that although the three-wire system cannot completely eliminate the influence of wire resistance like a congruent arm bridge, it can greatly reduce the additional error caused by wire resistance, and the resistance value obtained is more accurate. Therefore, the three-wire connection method is generally used in industry. >
>Four-wire system>
>The four-wire platinum resistance measurement method uses two additional test lines to provide a constant current, and the other two test lines measure the voltage drop of the platinum resistance. As long as the voltmeter input The impedance is high enough that little current flows through the voltmeter, so the voltage drop across the platinum resistor can be accurately measured and the resistance value can be calculated. When the accuracy requirements are high or the measured resistance value is very small, the four-wire connection method can be used to eliminate the measurement error caused by the resistance of the wires. >
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