Types Of Switches || Pressure Switch || Limit Switch || Proximity Switch
Pressure switch
Pressure switches are very important in plant control and instrumentation.
They are mainly used in control circuits and power circuits.
Pressure switches consists of diaphragms or bellows as the pressure-sensing element.
When the pressure is increase or decrease the switch contact will be changed, the switch is either healthy or unhealthy.
It is used in interlocking system in a plant.
Pressure switches are mainly used to control
Air
Water
Hydraulic oils
Set points
Pressure switches have two different Setpoints:
Increasing Pressure Setpoint
Decreasing Pressure Setpoint
These Setpoint is also called as Operating Point of the pressure switch
Inductive Proximity Switch
Inductive Proximity Switch is a device which is used as a switch without physical contact.
Inductive proximity respond to targets that come within the active range of their generated sensing fields.
These units are completely self-contained, and house a field generator, amplifier, and other necessary circuitry to accomplish electronic switching.
The devices are all solid state and have no moving parts that can wear out.
The electronic switches are not susceptible to contact contamination, contact erosion, or material transfer as are mechanical switches.
The inductive proximity switch is based upon the principle of an attenuated LC-oscillator.
The oscillator circuit coil generates a high frequency magnetic field.
This scattering field radiates from the proximity switch sensing face.
If this field is penetrated by ferrous or non-ferrous metals , energy is reduced and thereby the oscillator will be attenuated.
The result of changing current consumption is evaluated.
Limit Switch
A Limit switch is an electromechanical device. It consists of a lever that is connected to the set of contacts.
They are used for control of a machine, as safety interlocks, or to count objects passing a point.
When the object travels towards and comes in touch with the lever.
The limit Switch performs the contacts to make or break an electrical connection.
Standardized limit switches are industrial control components manufactured with a variety of operator types, including lever, roller plunger, and whisker type.
A Limit switch is used to convert this mechanical motion to an electrical signal to switch circuits.
The limit Switch has two positions:
Normally opened
Normally closed
It is used for plant automation or machine safety interlocking applications.