Voltmeter

A voltmeter is a device for measuring voltage in volts. The scale of voltmeters is calibrated in microvolts, millivolts, volts or kilovolts in accordance with the measurement limits of the device.
A voltmeter is connected to the electrical circuit parallel to the section of the electrical circuit in which the voltage is measured. Most often, measurements are carried out relative to a common point of the entire circuit or part of it.

Pic.1 An example of connecting a voltmeter to a circuit (upcoming)

To obtain the most accurate voltage value, the internal resistance of the measuring part of the voltmeter should be as large as possible (ideally infinite). In reality, cheap ones have a low input impedance - about 1 megaohm, so they introduce a large error in the measurement results. The most advanced voltmeters have an input impedance of 10 megaohms or more. The high input resistance of the voltmeter creates the unobvious effect of displaying a small voltage value when the input measuring wires of the device are not closed. This is due to the presence of electromagnetic interference in the external environment.

Pic.2 An example of a multimeter with high input impedance working with open and shorted wires (upcoming)

The history of the creation of a voltmeter is described in more detail - see - Invention of a “simple” voltmeter

Depending on the level of development of instrument making, the type of voltmeter was different. For example, in 1916, a voltmeter looked like a pocket watch of that time. (See more here)


Pic.3 A 1916 voltmeter

To build the first digital voltmeters, ICL7106 and ICL7107 from MAXIM were widely used.

The voltmeter should also be considered as a mode of operation of the multimeter.
At the same time, modern digital multimeters are built on the basis of a voltmeter circuit, which measures different voltages in different operating modes of the multimeter. The measured voltage values are displayed as values of other physical quantities (resistance, temperature, etc.).