Capacitive Proximity Switches

Capacitive Proximity Switches
Introduction
The capacitive Proximity Switches are designed for sensing wide range of materials. These switches give a superior performance for detection of various non-metallic objects where inductive type switches can not function.
Applications:

• Liquid Level
• Plastic granules & parts
• Sand / bulk material Ievel
• Food / Grain / Confectionery
• Paper and Rubber
• Glass Bottles / Tins in packaging

Working Principle
The switch works on the principle of resonant oscillator Ckt. A pair of Brass/ Copper disc form the electrodes of a capacitor and the object acts as a dielectric media. The change in capacitance value, due to presence of objects, is sensed by a precision integrated circuit.
Connection Diagrams
3-Wire & 4Wire DC
These switches operate on 10-30 V Dc and can be used with Logic Circuits, Counters or to drive Relay Coil directly. The output of there switches can be either PNP or NPN or both. The switching is in the sourcing mode and the load must be connected between the Output and the Negative of the supply. Conversely, with NPN output switching is in sinking mode & the load must be connected between the output & the positive of the supply.
All 3 wire & 4 wire DC switches are internally Protected against Inductive voltage peaks. Spurious Iine pulses, Reverse polarity short circuit conditions.

2-Wire DC
These switches are designed to operate external Loads connected in series with the switch. During operation, there is a voltage drop of about 6 V across the switch & the load connected in series gets the supply voltage reduced accordingly.
2-Wire AC
The AC switches are designed for 2 wire connected and operate on full line voltage. The loads are to be connected in series with the switch in a similar manner to that of a mechanical limit switch. The external PLC, Contactor, Relay etc. The operating (OFF state) current ofthese switches is less than 3 mA.
Generally the continuous load current should be restricted up to 60% of specified load current.