What are the types and characteristics of inductive sensors?
Inductance type sensor uses electromagnetic induction to convert the measured physical quantity such as displacement, pressure, flow, vibration, etc. into the coil's self-inductance coefficient and mutual inductance coefficient, and then converts the circuit into voltage or current change. The output is output to achieve non-electricity to power conversion.
A sensor consisting of a core and a coil that converts a change in linear or angular displacement into a change in inductance of the coil, also known as an inductive displacement sensor. The coil turns and the material permeability of the sensor are both constant, and the change in inductance is caused by the geometrical change of the magnetic circuit of the coil due to the displacement input. When the coil is connected to the measuring circuit and the excitation power is turned on, a voltage or current output proportional to the displacement input amount can be obtained.
Commonly used inductive sensors are variable gap type, variable area type and solenoid type. In practical applications, these three sensors are often made differential to increase linearity and reduce the additional error caused by electromagnetic attraction.
Variable Clearance Inductive Sensor The air gap δ of this sensor changes with the measured change, changing the magnetic resistance. Its sensitivity and nonlinearity decrease with increasing air gap, so it is often necessary to consider both. δ is generally between 0.1 and 0.5 mm.
Variable Area Inductive Sensor The relative coverage area (ie, the flux cross section) between the core and the armature of this sensor changes with the measured change, thereby changing the reluctance. Its sensitivity is constant and its linearity is also very good.
Solenoid-inductor sensor consists of a solenoid coil and a cylindrical armature that is connected to the object to be measured. The working principle is based on the change of magnetoresistance on the leakage path of the coil magnetic line. The armature changes the inductance of the coil as it moves. This sensor has a large measuring range, low sensitivity, simple structure and easy fabrication.
Inductive sensor features
(1) Sensitivity and resolution are high, and a displacement change of 0.01 μm can be measured. The output signal of the sensor is strong, and the voltage sensitivity is generally up to hundreds of millivolts per millimeter.
(2) The structure is simple, the sensor has no active electrical contacts, so the work has a reliable and long service life.
(3) Both linearity and repeatability are better. Within a certain range of displacement (several tens of microns to several millimeters), the sensor nonlinearity error can reach 0.05% "0.1%. At the same time, this sensor can realize long-distance transmission of information. , recording, display and control, it is widely used in industrial automatic control systems. However, it lacks shortcomings such as low frequency response and fast dynamic measurement and control. There are many types of inductive sensors, and common ones are self-inductive, mutual inductance and eddy current three.