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Measure voltage, current and signals

Measure voltage, current and signals

Measurement is useful only when it is clear what the instrument is actually measuring. Voltage is measured between two points; current flows through a path and therefore requires a different connection. An oscilloscope also has a reference connection that can be safety-critical on mains-powered equipment.

Start with the expected order of magnitude and then choose the instrument, range and connection method.

Questions on this page

Why must I not simply connect an ammeter in parallel with a power supply?

In current mode, a multimeter has a very low internal resistance. Connecting it in parallel can therefore create almost a short circuit and damage a fuse, meter or circuit. Current is normally measured in series or with a suitable current clamp or shunt.

What is the difference between measuring AC and DC?

DC concerns a steady component; AC concerns a varying component. With complex waveforms, the meaning of an AC measurement depends on the instrument and whether it measures true RMS. An oscilloscope can make the waveform visible.

When do I need an oscilloscope?

For timing, pulses, communication, ripple, oscillation or fast disturbances that a multimeter does not show. Choose bandwidth and probe to suit the signal and pay attention to the oscilloscope ground connection.

Where can I learn to measure safely?

The electricity workshop covers basic electrical knowledge; for electronic measurements, Electronics and Science and experiments are relevant.