Loading-Effects Reduction Using a Voltmeter in Series and an Ammeter in Parallel

This article proposes a method for reducing the loading effects when a dc voltage or current is measured in a linear circuit with a digital multimeter (DMM). In the proposed method, the voltmeter is placed in series to estimate the current, and the ammeter is placed in parallel to estimate the voltage, which is the opposite of the conventional approach. Its application is particularly of interest when the equivalent resistance between the nodes of the dc voltage (current) under measurement is high (low). In comparison with the conventional method, the relative error is up to a factor of 10(4) lower if the equivalent resistance equals the shunt (input) resistance of the DMM when a dc current (voltage) is measured.

Automated summary

This article proposes a method to reduce the loading effects in a linear circuit when measuring a dc voltage or current with a digital multimeter (DMM). In the proposed method, the voltmeter is placed in series to estimate the current, while the ammeter is placed in parallel to estimate the voltage, which is opposite to the conventional approach. This method is particularly useful when the equivalent resistance between the nodes of the measured dc voltage or current is high or low. Compared to the conventional method, the relative error is reduced up to a factor of 10(4) if the equivalent resistance matches the shunt or input resistance of the DMM during dc current or voltage measurement.