What is Proximity Sensor

Function

-         Sense distance of object
-     Differential conductive object from others

Principle of operation

1. High-freq oscillation type - use electromagnetic induction
1. Coil produce high-freq magnetic field
2. Object approach, eddy current induce in obj
3. Obj closer, current higher
4. Load on oscillation circuit higher
5. Detection and output
6. *Non-ferrous metal closer, oscillation freq lower, ferrous metal closer, osc freq higher.

2. Magnetic type – use magnetism

3. Electrostatic capacity type
1. sense changes in the electrostatic capacity btw sensing obj & sensor

Factor affecting sensing distance

1. Material of the object
1. Conductivity higher, magnetic induction lower
2. Non-ferrous metal more conductive, sensing distance smaller

2. Size of object
1. Size smaller, detection distance smaller

3. Thickness
1. For non-ferrous < 0.01mm, detection distance = ferrous metal
2. Magnetic metal must > 1mm.