A voltmeter is an instrument that finds wide application in measuring the electrical potential difference, called voltage, between two points in an electric circuit. Letter V in a circle is usually used to represent a voltmeter in an electrical circuit diagram.
Voltmeters are generally classified into two categories: Analog and digital. In analog voltmeter, a pointer across a scale gives indication of potential difference. A digital voltmeter (DVM) converts the measured voltage to a digital value and displays in numeric form. A DVM is designed around an integrating converter, which is a type of analog to digital converter.
A sensitive galvanometer (current meter) in series with a high resistance forms a basic analog voltmeter. The internal resistance of a voltmeter must be high to avoid it drawing significant current. If it uses more current, the function of the circuit being tested may be disturbed.
AC voltmeters are designed to use in alternating current (AC) circuits and DC voltmeters are used in direct current (DC) circuits. Radio Frequency (RF) altimeter is special kind of voltmeter.
There are voltmeters permanently mounted to panels like in generators and electrical panels. Portable instruments are mainly used in electrical and electronic work sites and electrical and electronic laboratories. Digital voltmeters are highly accurate compared to analog ones.
Andrew K is the inventor of digital voltmeter.