It is, but for the purposes of learning to use a voltmeter, simply checking from a known ground to a potential source of voltage is a good start. As long as a primary, non-computerized circuit ...

A multimeter and its test leads allow electrical workers to reach into an energized panel, touch live circuit components with the end of the test leads, and capture electrical readings like voltage, ...

These resistors don’t matter much because the voltmeter is essentially an open circuit. No current flows so, therefore, there’s no voltage drop across the leads.

If you want to measure voltage you reach for a voltmeter. Current? An ammeter. Resistance? An ohmmeter. But what about measuring AC power? A watt meter? Usually. But if you know what to do, you cou… ...

The DMR20-1-ACV "nanometer" self-powered four-digit bright LED voltmeter from Murata can measure the true RMS value of its input from 85 to 264 VAC to within 0.1 V resolution.