How a digital multimeter works
The basic principle of the multimeter is to use a sensitive magnetoelectric DC ammeter (microammeter) as the head. When a small current passes through the meter head of the multimeter, there will be a current indication. However, the meter head cannot pass a large current, so some resistors must be connected in parallel or in series on the meter head for shunt or step-down, so as to measure the current, voltage and resistance in the circuit.
