• AG Electronics

Inductive Proximity Switches

AG Electronics offers Inductive Proximity Switches that are non-contact type, solid state devices used to identify the presence of metal objects, speed measurements, position sensing, counting, etc. Operation: inductive proximity switch generates high frequency alternating field at the active face by the oscillator circuit. When any metal object is brought into the field it causes oscillation to stop, hence the demodulated voltage feeding the trigger disappears. The main sub-assemblies of the inductive switches are as follows: a) Oscillator (LC-resonant circuit), b) Trigger element, and c) Amplifier, output stage. DC inductive proximity switches: for DC switches the trigger operates rapidly when oscillation stops. This trigger switches the output, NPN/ PNP transistor to drive an electronic circuit or relay. AC inductive proximity switches: for AC switches a thyristor is triggered when oscillation stops. This thyristor is connected in series with a bridge and this series combination is connected to the AC load. Namur switches: these are 2-wire DC switches, designed in accordance with the DIN-19234 and Namur (working group of standards for measurements and control systems in chemical industry) which contains only oscillator and therefore require a separate amplifier. This is the most reliable of all types. When there is no target within the actuation distance, there is current through the load exceeding 3 mA. In the presence of the target the current falls to less than 1 mA. (Recommended nominal voltage 8 V DC and nominal value of series resistance is 1000 Ohms).