Voltmeters

A voltmeter is an instrument for measuring the electrical potential difference between two points in a circuit. To avoid perturbing the circuit, it is designed with high input impedance and is usable for DC or AC voltages. Readings are given in volts with specified accuracy and range.

Analog voltmeters typically rely on a moving-coil galvanometer plus a calibrated series resistor to convert voltage into a measurable current that moves a pointer. They require careful calibration and can suffer from parallax error, scale nonlinearity, and sensitivity to temperature and magnetic fields.

Digital voltmeters use analog-to-digital converters to display voltage numerically. They generally provide higher input impedance, can measure DC and AC, and may offer true RMS, auto-ranging, and data logging. Digital multimeters usually include a voltmeter function with additional features.

Key considerations include input impedance, loading effects, accuracy class, range selection, probe quality, and safe connection practices, especially at higher voltages. For precise work, buffers, differential probes, or voltage dividers may be used.

Voltmeter development progressed from galvanometer-based instruments in the 19th century to electronic and digital devices. Today voltmeters are essential in laboratories, industry, and consumer electronics, appearing as standalone meters and as functions within multimeters.