How Does an Analog Multimeter Work?
The heart of an analog multimeter is a D’Arsonval (or Weston) meter movement. This device uses DC current passing through a coil and magnet assembly to swing a pivot-mounted needle. The amount of current flowing through the coil determines how far the needle will swing. The selector dial on the front of the meter determines the type of filtering the test value will go through, whether it is fixed resistances, rectifiers or an internal voltage source. By using Ohm’s law (Voltage = Current * Resistance) and the current-indicating function of the D’Arsonval movement, the multimeter can indicate current (AC and DC), derive voltage (AC and DC) and, with an internal battery as a known voltage source, derive resistance values. DC Current or Voltage Settings When the meter is set to read DC current, the test value will go through limiting resistors to scale the current down for protection of the D’Arsonval movement. Otherwise, the current is applied directly to the D’Arsonval movement, and the
