Classification and application of inductive sensors

The theoretical foundation of inductance sensor application is electromagnetic induction, that is, using coil inductance or mutual inductance change to realize non-electric quantity measurement.Depending on the principle of electromagnetic induction, the change of measured physical quantity is transformed into the transformation of self inductance l or mutual inductance m.The former is called self inductance sensor, the latter is called mutual inductance sensor or transformer sensor.Inductive sensor has the advantages of simple structure, high resolution, small zero drift, good linearity, stable performance and shock resistance.The main disadvantages are the mutual restriction of sensitivity, linearity and measurement range, and the low frequency response of the sensor itself, which is not adapted for rapid dynamic measurement.It is commonly used in the measurement of displacement, pressure and flow in industrial automation.

Inductive sensor has the advantages of simple structure, fast dynamic response, easy to realize non-contact measurement and other prominent advantages, especially suitable for acid, alkali, chlorine, organic solvents, liquid CO2, ammonia and PVC powder, the ash, oil/water interface level measurement, such as in metallurgy, petroleum, chemical, coal, cement, food and other industries widely used.

Detect the attenuation of distance.Slip-warping is of iron, suitable for inductive sensor detection;The size of the tested part is slightly smaller than that of the standard test object (the standard test object size is 3 times the rated detection distance, in this application, the standard size should be 120*120mm), so there will be certain attenuation.Field anti-interference ability.This is an issue that cannot be ignored. Ordinary inductive sensor is easily interfered by motor or frequency converter, and many technicians only choose the sensor with potent anti-electromagnetic interference in the application nearby.However, in the automobile manufacturing workshop, the factory is large, and the technicians on site are utilized to communicate by interphone, especially when they talk on the interphone while walking, they will inadvertently get close to the sensor, resulting in temporary failure.

Installation aspects.With the popularization of inductive sensor, not only the electrical performance of the sensor has been improved, but also its mechanical design has become ever more humane.To achieve the most humanized installation.It reduces the stocking time of many similar products and decreases the time of installation and maintenance.Guarantee of stable operation.In the use of car factories, to prevent any oil, dust and pollution erosion.In addition, when the slip warping passes through the orbit, the vibration is long-term, and excellent seismic resistance also plays a key role.

There are various kinds of inductive sensors, which can be divided into variable reluctance type, variable air gap type (self inductance type), transformer type and eddy current type (mutual inductance type).M. array in the electromagnetic induction law (1831) pointed out that when a coil current I change, the current of the magnetic flux Φ changes, thus in the coil winding induction potential e, this phenomenon is called self inductance, the induced potential called self-induction electric potential.Variable magnetoresistive sensor belongs to self - sensing sensor.This type of inductance sensor is also called a variable air gap inductance sensor.It is comprised of coil, iron core and armature 3 parts.The iron core and armature are made of magnetic materials such as silicon steel sheet or other alloys, and there is just an air gap between the iron core and armature.

       When the measured part moves, the armature moves, and the change of air gap thickness changes accordingly, causing the change of magnetoresistance in the magnetic circuit, thus leading to the change of inductance value of the inductance coil. Therefore, as long as the change of inductance can be measured, the size and direction of the armature displacement can be determined, and the measurement of the measured part can be realized.The differential variable-gap inductance sensor consists of two identical inductors and magnetic circuits.During the measurement, the armature is related to the object under test. When the object under test moves up and down, the armature moves up and down with the same displacement. The magnetoresistance of the two magnetic