Signal coupling set to DC Signal coupling set to AC

When measuring DC voltages, make sure that the signal coupling is set to DC. This allows for both the AC and the DC components of the input signal to pass. Whether you're using the voltmeter, the oscilloscope or the transient recorder, your DC voltage should now be correctly displayed.

In contrast, if AC coupling is used, the DC component of the input signal is rejected and only the AC component is shown. This setting is particularly useful for investigating an AC ripple on a rather large DC component.

In the image above and below, channel 1 is set to DC coupling, while channel 2 is using AC coupling. Both channels are connected simultaneously to the function generator. As can be seen, channel 1 is accurately measuring a 5 volt DC signal, while channel 2 notes a 1.3 mVolt AC ripple voltage on the DC voltage.