A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel with the circuit, mainly because the same voltage drop occurs across it. A voltmeter usually has a high resistance so that it takes negligible current from the circuit. Voltmeters are made in a wide range of styles, some separately powered (e.g. by battery), and others powered by the measured voltage source itself. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus. Portable instruments, usually equipped to also measure current and resistance in the form of a multimeter, are standard test instruments used in electrical and electronics work. Voltmeters operating on the electrostatic principle use the mutual repulsion between two charged plates to deflect a pointer attached to a spring. Meters of this type draw negligible current but are sensitive to voltages over about 100 volts and work with either alternating or direct current.
To use a voltmeter, you need to connect it in parallel to the device you want to measure the voltage of. Voltmeters are connected in parallel with the circuit, and they are made in a wide range of styles, some separately powered (e.g. by battery), and others powered by the measured voltage source itself. Before using a voltmeter, you need to determine whether the current youre measuring is a direct current (that flows in one direction) or an alternating current (that flows back and forth) . Make sure youre using a voltmeter thats compatible with the type of current youre measuring, or that your voltmeter is set to the appropriate setting.
