Inductance Sensor

a measuring transducer that converts an angle of rotation or a displacement into a change in inductance. An inductance sensor is an inductance coil and a magnetic circuit whose movable element (armature) is displaced by the action of the quantity being measured. Since the air gap and hence the reluctance of the magnetic circuit undergoes a change, the inductance of the coil is also changed. For measurement, the coil of the inductance sensor is connected to an AC (differential or bridge) circuit. In such a circuit the indicating component is calibrated in units of the quantity being measured.

Inductance coils with a variable gap or a variable gap area are used most frequently. The first type is used in measuring small displacements (from fractions of a micron to 3–5 mm); the second variant is used for displacements in the range from 0.5 to 15 mm. Inductance sensors whose inductance coils are connected to a high-frequency power supply (5–50 MHz) or are used as windings in high-frequency oscillatory circuits are used to measure displacements in low-power devices (such as pointer-type meters).