Phase measurement

The phase is the subject of numerous measurement methods, which are used in a wide variety of fields.

• In the context of high currents, let's mention the importance of the power factor for the qualitative definition of an electrical installation, the need for phase control when coupling two networks, the value of measuring the internal angle of synchronous machines under disturbed conditions and recording the transient phase difference between the voltages and currents of an asynchronous motor during start-ups, etc.

• In weak current technology, phase is as fundamental a parameter as amplitude, and can sometimes become a crucial point: it needs to be monitored, conditioned, advanced or delayed with care and caution; let's mention the role of phase in servo systems, data acquisition and transmission chains, telephone lines, television, radar technology, space telecommunications, etc.

• Phase measurement should not be restricted to electrical phenomena alone: using transducers, physical quantities can be transformed into electrical voltages, enabling us to study fluid propagation or mechanical vibration phenomena; for example, by measuring the modulus and phase of a mechanical impedance at different points on a structure, we can understand the structure's resistance to vibration, with a view to locating nodal points and lines in continuous mechanical constructions, or determining resonance frequencies, modulus of elasticity and loss factor, or minimizing vibration transmission . These are just some of the problems involved in building modern, high-quality machines.

  From high current to low current, of all types and frequencies, many principles of phase difference measurement have been proposed, using a wide variety of setups, each often responding to specific constraints and producing measurements with well-defined meanings.