• Introduction

A pressure switch is a fundamental safety and control device designed to automatically open or close an electrical circuit when a specific fluid or gas pressure reaches a predetermined set point. Unlike a gauge that provides continuous measurement, the switch acts as a binary operator, utilizing a sensing element—such as a bellows, diaphragm, or piston—that physically moves against a calibrated spring to trigger a micro-switch. When the process pressure overcomes the spring force, the switch changes state (either Normally Open or Normally Closed), allowing it to perform critical functions such as activating alarms, starting or stopping pumps, or initiating emergency shutdowns. This makes it an essential component in industrial systems for maintaining pressure within safe operating limits without the need for constant human intervention.

  • Working Principles

The working principle of a pressure switch centers on the mechanical balance between process pressure and a pre-tensioned internal spring. When fluid or gas enters the sensing chamber, it exerts force against a sensing element—typically a diaphragm, bellows, or piston—which is held in place by a range spring adjusted to a specific “set point.” Once the process pressure exceeds the opposing spring force, the sensing element shifts, moving a plunger that physically trips an electrical micro-switch to change the circuit from its normal state. As the pressure drops below a certain level, known as the deadband or reset point, the spring force pushes the element back, resetting the switch. This mechanical action allows the device to automatically trigger external equipment, such as motors or alarms, based entirely on real-time pressure thresholds.

  • Applications

Pressure switches are essential for automated control and safety, acting as the primary defense against over-pressurization or system failure.

  • Pump and Compressor Control

  • Emergency Shutdown (ESD) Systems

  • HVAC Systems

  • Hydraulic Systems

  • Low-Level Alarms

  • Boiler and Pressure Vessel Safety

  • Process Interlocking

  • Filter Monitoring

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