How would you verify a DC supply’s voltage under load?

• A. With the equipment under operating load, measure the voltage at the supply terminals using a multimeter or oscilloscope to check for voltage drop and ripple.
• B. Measure the voltage with the circuit powered off to verify no load.
• C. Use a megger to check under load.
• D. Measure resistance of the supply under load.

Answer: (A)

When a DC supply is delivering current to a load, the actual voltage can dip and ripple away from the nominal value depending on the supply’s regulation, wiring, and contacts. To verify this, measure the voltage while the equipment is operating and drawing current, at the supply terminals or right at the load, so you see the real conditions the electronics experience. Use a multimeter for a steady DC level and an oscilloscope if you need to check ripple and transient behavior, which can affect precision or cause interference. If you find voltage sag or significant ripple, it points to regulation issues, inadequate current capability, or losses in wiring/connectors that need addressing. Measuring with the circuit powered off only shows no-load conditions, which isn’t what you want for under-load verification. A megger tests insulation, not voltage under load. Measuring resistance under load doesn’t tell you the actual voltage behavior the load receives.