Discrete Event Sensors
Some common discrete event sensors utilized in manufacturing are mechanical limit switches, proximity sensors & photoelectric sensors.
- Mechanical Limit Switches
Mechanical limit switches comprises a mounted actuator arm that operates a set of electrical contacts while the arm is placed. The electric contact might either be closed or open initially and the action of the actuator & lever arms takes it from its normal, or deactivated, state to the other state. Limit switches come in various varieties and designs. They are designed for heavy-duty application in which there is physical contact among the actuator & the process being sensed. For instance, limit switches are frequently utilized on machine tools to limit the travel of a machine axis. They are sometimes utilized in material handling application. They are designed to handle comparatively high voltages, both AC and DC.
Proximity switches refer to a non-contact sensor that works on the principle of a magnetic field. The proximity switches most commonly utilized in the manufacturing environment are the inductive proximity switch & the capacitive proximity switch. Proximity switches have comparatively short sensing ranges typically from 1 to 60 mm; thus, they ought to be used in situations where the target is permitted to come close to the sensor.
Photoelectric sensors are non-contact devices that output a signal in response to the interruption of a light beam. The two major components are the receiver and the emitter. The light source is a light emitting diode (LED). A photoelectric sensor system comes with an oscillator that modulates, or pulses, the LED on and off at very high frequencies. They are designed for utilizes in four basic sensing modes: retro reflective, opposed diffuse, and convergent. The suitable sensing mode based on the application. Photoelectric sensors have the ability of being utilized over a fairly long distance. For instance, distances over 100 feet are possible in an opposed sensing modes.
This device is analogous to a limit switch in mechanical systems. They are employed in procedure industries as a device to detect while a fluid travelling in a pipe is over a particular volumetric flow rate. Such a sensor might be used to govern the speed of an upstream pump, reducing it while the flow is too fast.