scientist with test tubes

A vector voltmeter is a type of electrical test equipment that indicates the level and phase difference between the first and second inputs. It is a specialized voltmeter capable of measuring vector properties. A vector voltmeter is part of a wide range of test equipment known as vector meters. Vector meters are usually found in electrical design laboratories and special monitoring panels.

Vector and scalar are two common representations of real-world quantities of various entities. The scalar unit has no direction, or the direction is implied. For example, a mass of 11 lb. (5 kg), a scalar, will have a weight of 5 kg, a vector. The direction of the 5 kg weight is implied as downwards, and the weight of an object is also a vector because weight is a force pointing downwards.

Scalar quantities have only magnitude, while vector quantities have both magnitude and direction. When the voltage of a 1.5 volt (V) battery is measured with a voltmeter, the result reads as “1.5 V. positive.” When another battery is measured in series, the result can be read as “3, 0 V. positive” If a battery in the series connection has been reversed, the reading becomes 0 V. This is called vector cancellation.

Vector cancellation occurs when two vectors of the same magnitude but opposite direction are added. Vectors can add or cancel each other fully or partially. Real-world vectors will not be exactly in-phase or out-of-phase. The phase difference will range from 0 to 360 degrees.

A vector voltmeter is capable of measuring the vector difference between two voltage sources. An example is a three-phase power supply where the three outputs are 120 degrees phase apart. A vector voltmeter will be able to confirm the phase difference between the outputs. The so-called phase-to-neutral voltage can also be obtained.

Reactive components in electrical and electronic circuits produce a phase shift in the time-varying signals that are introduced. A phase shift can be anywhere between 0 and 360 degrees. Currents and voltages in capacitors or capacitors and inductors tend to have phase differences of 90 degrees. These reactive components in various circuit combinations produce a wide range of possible phase differences at different frequencies.

Another use of the vector voltmeter is measuring the frequency and phase response of electronic amplifiers. The equipment’s frequency response can be plotted by measuring and plotting the input and output levels at various test frequencies. By measuring the input and output phase relationship at various frequencies, the phase response can also be plotted as a guide in implementing additional circuit stages to obtain the desired overall characteristics.