Fasemeters

Fasemeters are measurement instruments designed to determine phase relationships between electrical signals, particularly the phase angle and phase difference between voltage and current in alternating-current systems. The term is uncommon in standard electrical engineering usage; many sources refer to these devices as phase meters, phase-angle meters, or vector voltmeters. Fasemeters can be analog or digital, handheld or benchtop, and often support multiple input channels to compare two or more signals concurrently.

Core functions include detecting the phase of periodic signals, computing the phase difference between inputs, and displaying results in degrees or radians, with optional readouts for power factor and phase sequence. Most fasemeters rely on sampling and digital signal processing, deriving phase from techniques such as zero-crossing analysis, Fourier or Hilbert-transform methods, or equations that track the fundamental component. For non-sinusoidal waveforms, some fasemeters report the phase of the fundamental component or provide time-domain phase metrics.

Typical applications include laboratory testing, electrical-grid monitoring, synchronization of generators and inverters, motor control and drive diagnostics, and protection schemes that depend on phase information. Fasemeters may be standalone instruments or part of more comprehensive power meters and phasor measurement systems. In power-system contexts, adjacent devices like phasor measurement units (PMUs) and vector voltmeters serve related roles and may offer wider sampling and communication capabilities.

Limitations involve accuracy dependent on sampling rate and clock stability, noise sensitivity, and the treatment of non-stationary or highly distorted signals. Calibration and proper input conditioning are important for reliable results.