In the same manner the potentiometer may be used to calibrate a voltmeter by the aid of a divided resistance of known value.
In this case a highresistance wire is connected between the points of which the potential difference is required, and from some known fraction of this resistance wires are brought to an electrostatic voltmeter, or to a movable coil electromagnetic voltmeter, according as the voltage to be measured is alternating or continuous.
Utilizing this principle many inventors have devised forms of electrostatic voltmeter.
Numerous forms of hot-wire or thermal voltmeter have been devised.
A high-resistance electrodynamometer may be employed as a voltmeter.