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Non-Contact Presence Sensors (Proximity Sensors)
Limit switches, discussed earlier are "contact" presence sensors, in that they have to be touched by an object for that object's presence to be sensed. Such contact sensors are often avoided in automated systems because whenever parts touch there is wear and a potential for eventual failure of the sensor. Automated systems are increasingly being designed with non-contact sensors. The three most common types of non-contact sensors in use today are the inductive proximity
sensor, the capacitive proximity sensor, and the optical proximity sensor. All of these sensors are actually transducers, but they include control circuitry that allows them to be used as switches. The circuitry changes an internal switch when the transducer output reaches a certain value, and the output of the switch becomes the control systems proximity sensor.
Each of these fundamental types is explained by following the menu links on the left. |
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