# Pressure Switch

Written by Jerry Ratzlaff on . Posted in Pressure Instrument

## Pressure Switch

A pressure switch ( $$PS$$ ) provides a discrete input to the PLC.  The pressure switch is typically used as a method of control in tanks, vessels and over all process control.

Note that a pressure switch is different than a pressure transmitter in that a pressure switches sole function is to provide a binary TRUE or FALSE into the PLC.  This approach simplifies programming.

## Types of Pressure Switches

• Mechanical Deflection
• Piston
• Strain Gauge
• Semiconductor Piezoresistive
• Piezoelectric
• Thin Film
• Variable Capacitance

## Configuration and Alarms

Configuration (Normal State):

• $$NO$$ - Normally Open
• $$NC$$ - Normally Closed

Alarms in the PLC can be:

• $$PSH$$ - Pressure Switch High
• $$PSL$$ - Pressure Switch Low
• $$PSHL$$ - Pressure Switch High/Low