Industry continually strives to develop product faster and more cost effectively. By automating processes, manufacturers can realize these goals while maintaining higher levels of quality and reliability. Presence sensing technology is used to monitor, regulate and control these processes. More specifically, presence sensors help verify that critical process steps are completed as intended.
The chapters we will discuss about basic operating principles common to all sensors their application.
- Limit Switch
- Inductive Proximity Sensor
- Capacitive Proximity Sensor
- Ultrasonic Proximity Sensor
- Photoelectric Sensor
Now What is a sensor ?
A sensor is a device for detecting and signalling a changing condition. And what is this “changing condition”? Often this is simply the presence or absence of an object or material (discrete sensing). It can also be a measurable quantity like a change in distance, size or color (analog sensing). This information, or the sensor’s output, is the basis for the monitoring and control of a manufacturing process.
1. Limit Switch
A limit switch is an electromechanical device that consists of an actuator mechanically linked to a set of contacts. When an object comes into contact with the actuator, the device operates the contacts to make or break an electrical connection.
Limit switches are used in a variety of applications and environments because of their ruggedness, ease of installation, and reliability of operation. They can determine the presence or absence, passing, positioning, and end of travel of an object. They were first used to define the limit of travel of an object; hence the name "Limit Switch."
Limit Switch Construction
Limit switches are designed in two body types: plug-in and non plug in. The sub assemblies which make up a limit switch are described below.
Limit Switch Construction
Basics Components :
- Actuator : The actuator is the portion of the switch that comes in contact with the object being sensed.
- Head : The head houses the mechanism that translates actuator movement into contact movement. When the actuator is moved as intended, the mechanism operates the switch contacts.
- Contact Block : The contact block houses the electrical contact elements of the switch. It typically contains either two or four contact pairs.
- Terminal Block : The terminal block contains the screw terminations. This is where the electrical (wire) connection between the switch and the rest of the control circuit is made.
- Switch Body : The switch body houses the contact block in a plug-in switch. It houses a combination contact block and terminal block in the non plug-in switch.
- Base : The base houses the terminal block in a plug-in switch. Non plug-in switches do not have a separate base.
Non plug-in Housings
The first housings developed were the non plug-in type. They are box shaped with a separate cover. Seals between the head, body, and cover are maintained by an O-ring and a flat gasket. Non plug-in style limit switches are offered in a wide range of styles conforming to IEC or NEMA specifications.
Non plug-in Housing
to be continued tomorrow cause I'm sleepiness...........
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