Inductive sensor principle Inductive sensor classification

Inductive sensor, which mainly uses the principle of electromagnetic induction to convert the measured physical quantity such as displacement, pressure, flow and vibration into the self-inductance coefficient and the mutual inductance of the coil, and then converted by the circuit into the voltage or current. Output, to achieve non-electricity to power conversion. The following small series introduces the principle of inductive sensors and classification of inductive sensors.

Inductive sensor principle

The basic principle of inductive sensors is the principle of electromagnetic induction, which uses electromagnetic induction to convert the measured non-electricity (such as pressure, displacement, etc.) into a change in inductance, and then converts the change in inductance to voltage by measuring the conversion circuit. The current changes to achieve non-electricity measurements. Such inductors include variable air gap inductors, differential solenoid inductors, differential transformer inductors, and eddy current inductors.

Inductive sensor classification

Commonly used inductive sensors have variable-gap type, variable-area type and follower type. In practical use, these three types of sensors are often made in differential type in order to improve the linearity and reduce the additional deviation caused by electromagnetic attraction. The air gap of the variable-gap inductive sensor changes with the change in measurement to change the magnetic resistance. Its sharpness and non-linearity decrease with the increase of air gap, so it is often necessary to consider both. The absolute cage area between the iron core and the armature of the variable area type inductive sensor changes with the change in measurement, thereby transforming the magnetic resistance. Its acuity is constant and its linearity is also very good. A solenoid-inserted inductive sensor is formed by a solenoid coil and a cylindrical armature connected to an object to be measured. The task principle is based on the change of the magnetoresistance of the magnetic circuit on the coil. The armature changes the inductance of the coil as it moves with the object being measured. This sensor has a large range, low sensitivity, simple structure, and ease of manufacture. In view of the above three kinds of sensors made of differential type, inductive sensors are basically divided into variable reluctance sensors - self-inductance; differential transformer sensor - mutual inductance; eddy current sensor - eddy current three varieties type.

A differential transformer type sensor is a sensor that converts a measured non-electrical change into a change in coil mutual inductance. Measurement accuracy, high sensitivity, simple structure, reliable performance.

Eddy-current sensors use eddy-current effects—when a bulk metal conductor is placed in a changing magnetic field or when a magnetic force line is cut in a magnetic field, a vortex-like sensation of current will occur within the conductor.

Inductive sensor requirements

1, the attenuation of the detection distance. Slippery is iron, suitable for inductive sensor detection; and the size of the warped measured part is slightly smaller than the standard test object size (standard test object size is 3 times the rated detection distance, in this application, the standard size should be 120*120mm ) In that case, there will be a certain amount of attenuation.

2, on-site anti-jamming capability. This is a problem that can not be ignored. Common inductive sensors are easily disturbed by motors or inverters. Many technicians only choose sensors with strong anti-electromagnetic interference for applications in this area. However, in the automobile manufacturing workshop, the factory building is large, and the on-site technicians are accustomed to using the walkie-talkie to communicate. In particular, when talking on the walkie-talkie while walking, they will inadvertently approach the sensor, resulting in temporary failure.

3, the installation. With the popularization of inductive sensors, sensors have not only improved in electrical performance, their mechanical design has become more humane. To the greatest degree of humane installation. Reduced the availability of multiple similar products and reduced installation and maintenance time.

4. Safe operation guarantee. In the use of the depot, we must eliminate any erosion of oil and dust. In addition, the vibration is a long-term existence when the gliding passes through the track, and the excellent anti-vibration also plays an important role.

Inductive sensor features

1, the structure is simple, the sensor has no active electrical contacts, so the work is reliable and has a long life.

2. With high sensitivity and resolution, it can measure the displacement change of 0.01 micron, and its output signal is strong, and the voltage sensitivity is generally up to several hundred millivolts of output per millimeter of displacement.

3, linearity and repeatability are better, in a certain range of displacement, the sensor nonlinear error of up to 0.05% ~ 0.1%.

Editor's summary: The inductive sensor principle and the inductive sensor classification are introduced here, and we hope to help everyone. If you want to know more about yourself, you can follow the information on this site.

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