Proximity sensor ,as the name implies ,it senses the proximity of an object .Or presence of an object . Proximity sensors doesn’t require physical contact with the object .The sensors may be inductive ,capacitive ,photosensitive etc. This article explains about inductive proximity sensors .
Inductive proximity sensor works on the principle of electro magnetic induction .And they are only applicable for detecting objects which are conducting .Because induction happens on conductors .They are also called eddy current Sensors .
Working
A inductive proximity sensor basically consists of the following circuitry
1 . oscillator circuit for generating high frequency RF field(Radio frequency)
2.Sensing circuit to detect the change in amplitude and triggering
3.Output circuit which generates a switched output .Using this output we can interpret the objects presence or absence .
The oscillator circuit creates high frequency RF field which radiates through the face of the sensor .And these oscillations have a defenite amplitude when no objects present nearby. When a metallic object approaches the sensor and get close to it ,an eddy current creates on this metal object due to induction This causes extra load to the oscillator driving circuit .And amplitude of the oscillation decrease .So the decrease in amplitude of the oscillation to a minimum level is interpreted as the presence of object .
The sensing circuit detects this change .And an output is triggered through the output circuit .
Applications of inductive proximity sensor
1.sensing moving machinery parts .
2.counting objects applications like that in packaging industries
3.Detecting rotary motion
etc
