The method of measuring resistance with digital multimeter-feeder resistance compensation measurement method
The feeder resistance compensation method is another common high-precision measurement method for multimeters to measure resistance. In the industrial field, if a high-precision resistance test is required, the three-wire connection method is often chosen, so that the measured resistance is connected to the grounding line. connected. The principle of this test method is shown in Figure 3. When using this technique for measurement, the current I is 800μA~1mA, R is the extremely low temperature drift wirewound resistance (if I=1mA, R=5kΩ), the temperature drift and time drift of the current I are equivalent to the MAX6250. level.
Principle of digital multimeter measuring resistance _ how to measure resistance with digital multimeter _ steps to measure resistance with digital multimeter
Principle of digital multimeter measuring resistance _ how to measure resistance with digital multimeter _ steps to measure resistance with digital multimeter
It can be seen from the above formula that in the process of feeder resistance compensation measurement, the additional voltage on the feeder resistance is added to the input end of A3 and eliminated by calculating the difference. The output voltage is only related to the measured resistance and has a linear relationship. Errors are fully compensated regardless of the size of the resistance being measured. This is why this measurement method can ensure that the resistance measurement results of the digital multimeter remain highly accurate.
In this feeder resistance compensation method to measure the small resistance circuit, the measurement accuracy mainly depends on whether the accuracy of the constant current source current I and the size of the feeder resistance RL are equal. The operational amplifier in the circuit can choose four general-purpose single operational amplifier (LM324). When using this method to measure resistances with a resistance value of less than 0.5Ω, make sure that the RLs are exactly equal.
