Ammeter

From the feedback from our readers we have learned that the measurement of currents in the positive lead of a power supply is often fraught with practical difficulties. The circuit shown here will in many cases be a welcome aid. The design is not really new, but it is very useful.The required shunt or current measuring resistor R1 is connected in series with the load. The voltage drop across this resistor is proportional to the current through the load. As usual, the opamp will strive to minimise the potential difference between its inverting- and non-inverting inputs.