By William Hirsch, Updated Mar 24, 2022
Every electrical system relies on precise current control. Engineers achieve this by incorporating resistors, whose resistance is measured in ohms. According to Ohm’s Law, a higher resistance limits current flow, which is crucial for protecting components such as blower motors. Resistors typically display their nominal value and tolerance—a range within which the actual resistance may vary. Verifying that a resistor falls within its tolerance ensures reliable operation.
Turn on your digital multimeter and set it to the resistance (Ω) mode, indicated by the Greek letter omega.
Place the black probe on the wire leading from the resistor’s left side and the red probe on the wire from the right side.
Observe the display. If the reading lies within the resistor’s tolerance band, the component is functioning correctly. For example, a 200 Ω resistor with a ±5 Ω tolerance should read between 195 Ω and 205 Ω.
Always double‑check that the meter is set to an appropriate range and that the resistor is not under load during testing to avoid inaccurate readings.
