By Carlos Mano Updated Mar 24, 2022
Analog multimeters feature a moving needle that aligns with a calibrated scale behind it. The needle’s position indicates the measured value—voltage, current, or resistance—once the selector knob is set to the appropriate range. While they are generally less expensive than digital units, analog meters offer tactile feedback that many technicians find invaluable for troubleshooting subtle circuit behaviors.
To capture the current flowing through a circuit, insert the meter in series with the component or path you wish to test. This requires breaking the circuit, connecting the meter’s leads in place, and ensuring a continuous current path. The meter’s internal battery drives a small test current; the needle position then reflects the ampere value. For quick calculations, use Ohm’s law: I = V / R.
For voltage measurements, connect the meter’s probes across the two points of interest. The meter reads the potential difference—the electric pressure—between the probes. If both probes touch the same point, the reading will be zero. Across a fresh 9 V battery, you should see a value near 9 V. When measuring across a component, the voltage drop indicates how much of the supply is consumed by that element.
Before measuring resistance, power the circuit off and isolate the component. The analog meter’s battery applies a low test voltage across the leads, producing a current that the meter interprets to display resistance. Use Ohm’s law in reverse: R = V / I. Note that accuracy depends on the meter’s internal zero adjustment.
Start with the meter set to its highest range. If the needle stalls, step down one range at a time until a clear reading appears. This routine protects the meter from overload and extends its lifespan.
Zero adjustment is essential for reliable resistance readings. With the leads together, turn the zero‑adjust knob until the needle rests at the zero mark before taking any measurement.
