What basic measurements would you perform with a digital multimeter on a control circuit to diagnose a problem?

• A. Continuity, resistance, and voltage at key points in the circuit.
• B. Capacitance and inductance readings.
• C. Frequency response of the control signal.
• D. Power factor of the load.

Answer: (A)

The essential approach is to use a digital multimeter to verify the actual electrical conditions at points in the control circuit: measure voltage to confirm proper power and signal levels, measure resistance to check component values and detect opens or shorts, and use continuity to confirm a solid path between points. These three checks quickly reveal common faults such as no power at a sensor, a blown fuse causing open circuitry, or a wiring break creating an open circuit. Capacitance and inductance readings are not typically obtained with a standard DMM; you’d need an LCR meter for those. Frequency response and power factor aren’t measured by a basic DMM either; they'd require an oscilloscope or a power-quality instrument. So you’d rely on voltage checks, resistance values, and continuity to diagnose most control-circuit problems.