Inductive Proximity Switches

When an application calls for detecting a metallic target that falls within an inch of the sensing surface, inductive proximity sensors are apt for the task. First introduced in the early 1960s, these durable components have proven their mettle in the sensing arena. In fact, they're the best-selling sensing technology in the world. Their immunity to dust and dirt buildup suits them well for harsh industrial environments. Additionally, the standardized physical and electrical characteristics of the general-purpose, cylindrical types of these sensors simplify their use.
An inductive proximity sensor has four components: the coil, oscillator, detection circuit, and output circuit. The target material, environment, and mounting restrictions all have an influence on these items and on the senor's operation, magnetic nature, and shielding. The oscillator generates a fluctuating, doughnut-shaped magnetic field around the winding of the coil, which is located in the device's sensing face. When a metal object moves into the sensor's field of detection, Eddy currents build up in the object, magnetically push back, and finally dampen the sensor's own oscillation field. The sensor's detection circuit monitors the amplitude of the oscillation and, when it becomes sufficiently damped, triggers the output circuitry.

There are five categories of inductive proximity sensors: cylindrical, rectangular, miniature, harsh environment, and special purpose. Cylindrical threaded-barrel sensors account for 70% of all inductive proximity sensor purchases. Years ago, this style's behavior was standardized by the CENELEC organization, which determined characteristics such as body size, sensing distances, and output levels.

Inductive Proximity switches can come in many shapes and sizes. The most common is a cylindrical switch or sensor, in 12, 18 or 30 mm. Other styles are flat pack, limit switch style, and slot. Switches normally sense from 2mm to 10 mm. Longer ranges can be used, but may need to be an unshielded switch.

Manufacturers are Pepperl and Fuchs, Autonics, ATC, Carlo Gavazzi and EMX.

Please visit our web site for Proximity switches.

Anderson-Bolds