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 10⁴ lower if the equivalent resistance equals the shunt (input) resistance of the DMM when a dc current (voltage) is measured.