What Is a Vector Voltmeter?

A vector voltmeter is a type of electrical test equipment that indicates both the level and difference in phase between the first and second input. It is a specialized voltmeter that is able to measure 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 instance, an 11 lb. (5 kg) mass, a scalar, will have a 5 kg weight, a vector. The direction of the 5 kg weight is implied as downward, and the weight of an object is also a vector because weight is a force pointing downward.

Scalar quantities only have 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 is read as “positive 1.5 V.” When another battery is measured in series, the result may be read as “positive 3.0 V.” If one battery in the series connection has been reversed, the reading becomes 0 V. This is called vector cancellation.

Vector cancellation happens when two vectors of the same magnitude but opposite direction are added together. Vectors may add or cancel each other totally 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 able to measure the vector difference between two voltage sources. One example is a three-phase power source where the three outputs have a 120-degree phase difference relative to each other. A vector voltmeter will be able to confirm the phase difference between the outputs. The so-called phase-to-neutral voltage may also be obtained.

The reactive components in electrical and electronic circuitry produce a phase shift in the time-varying signals that are introduced. A phase shift can be anywhere between 0 and 360 degrees. The currents and voltages in condensers or capacitors and in 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 the measurement of the frequency and phase response of electronic amplifiers. The frequency response of equipment can be plotted by measuring and plotting the input and output levels at various test frequencies. By measuring the phase relationship of input and output at various frequencies, the phase response may also be plotted as a guide in implementing additional circuit stages to obtain the desired overall characteristics.