5 Electrical Measurement and Safety Free Online FlashCards

Which three instruments’ functions does a DMM combine?

A digital multimeter combines the functions of a voltmeter, ammeter, and ohmmeter.

How should a voltmeter connect to the points being measured?

Connect a voltmeter in parallel across the component or two points being checked.

Which voltage modes correspond to AC and DC?

Select V~ for AC voltage or V⎓ for DC voltage. If the value is unknown and the meter is not autoranging, start above the expected voltage.

What does a negative sign usually indicate in a DC voltage reading?

A negative sign usually means the probes are reversed relative to the DC polarity.

How is a conventional DMM connected to measure current?

A conventional DMM measures current in series, so the circuit must be opened and the meter inserted into the current path.

Why must a DMM in current mode not be connected across a voltage source?

The current input has low resistance. Connecting it across a voltage source can cause a short circuit, blow the meter’s fuse, or cause injury.

What should you do before restoring power for a DMM current measurement?

Switch off power, use the correct fused current jack and mode, and confirm the setup is safe and within the meter’s limits before restoring power.

What should a clamp meter surround to measure current in a typical two-wire cable?

Clamp around a single conductor. Clamping around both conductors of a typical two-wire cable can make their magnetic fields cancel and mislead the reading.

What condition must a circuit meet before resistance testing?

Measure resistance only on a de-energized circuit. Disconnect power, verify it is off, and discharge capacitors according to safe procedures before testing.

What can an OL indication mean during resistance measurement?

OL or a similar indication often means resistance is beyond the selected range or the path is open; check the meter manual for its display conventions.

What does a continuity indication establish?

It indicates a path with resistance sufficiently low for that meter; it does not prove the whole circuit functions correctly.

Why might an in-circuit resistor reading be affected by other components?

Connected components can create other paths that affect the reading. If needed, isolate one resistor lead before measuring.