Key Takeaway
A pressure switch is a control device that activates or deactivates an electrical circuit when a preset pressure threshold is reached. It contains a sensing element—typically a diaphragm, piston, or bellows—which moves when exposed to system pressure. This mechanical movement trips a contact switch that can turn equipment on or off. Pressure switches are used in water systems, air compressors, hydraulic machinery, and industrial automation. They act as safety or control devices to prevent equipment damage or to maintain consistent operation. Available in both mechanical and electronic versions, they are reliable, compact, and essential in many pressure-based applications.
Definition and Core Function
A pressure switch is a device that activates or deactivates an electrical circuit when a preset pressure is reached. Unlike a gauge, which shows the pressure, a switch acts on it.
You can set a pressure threshold — when the system reaches that value, the switch triggers a contact. It’s used to control pumps, compressors, alarms, and even emergency shutdowns.
The core function: automatic control based on pressure. It ensures your process runs safely without manual intervention. Simple, effective, and essential in industrial automation.
Differences Between Pressure Switches and Pressure Gauges
Though they measure the same physical quantity, pressure switches and gauges serve different purposes.
Gauges show pressure values continuously — they are monitoring tools.
Switches trigger an action (ON/OFF) when pressure crosses a preset threshold.
For example, a gauge shows that pressure is 7 bar. A pressure switch turns off a compressor if pressure goes above 8 bar.
Use both in tandem — the gauge for monitoring, the switch for control. Don’t confuse one for the other. Misuse can lead to automation failures or unsafe operating conditions.
Types of Pressure Switches (Mechanical, Electronic)
Pressure switches are either:
Mechanical: Use springs, diaphragms, and snap-action contacts
Rugged, no power needed, lower cost
Electronic: Use sensors, relays, or transistors
Higher accuracy, programmable, remote monitoring
Applications:
Mechanical: Compressors, pumps, HVAC
Electronic: PLC integration, alarms, precision systems
Choose mechanical for simplicity, electronic for automation. Both types serve vital roles in process control and safety loops.
Common Applications in Control Systems
Pressure sensors are key inputs in industrial control systems. They:
Enable automatic pump shutoff
Trigger alarms for abnormal conditions
Maintain pressure within safe operating limits
Help modulate valves in PID loops
Examples:
Water treatment: Backwash triggered by filter pressure
Boilers: Fuel valve cut-off at overpressure
Pneumatic systems: Start compressors below 5 bar, stop above 8 bar
Digital transmitters and pressure switches are widely used for signal output to PLCs, SCADA, and building management systems. Precision control relies on reliable pressure feedback.
How Pressure Switches Improve System Safety
Pressure switches trigger an electrical response when pressure crosses a set point. Unlike gauges, they don’t display readings — they act.
Used in compressors, hydraulic lifts, fire suppression, and HVAC, they:
Prevent overpressure by shutting off equipment
Trigger alarms or venting when limits are breached
Automate processes based on pressure
For example, in an air compressor, a pressure switch may cut power at 120 psi and resume at 90 psi — maintaining safe pressure levels.
Modern switches offer digital set points, hysteresis control, and remote alerts. In safety-critical systems, they’re often paired with gauges to offer both monitoring and action.
Conclusion
A pressure switch monitors system pressure and triggers actions—like shutting off a pump or sounding an alarm—when preset limits are crossed. It doesn’t just indicate pressure like a gauge; it reacts. In boilers, compressors, and hydraulic systems, this automatic response prevents overpressure, overheating, or vacuum failure. Think of it as a safety circuit that ensures your process stays within safe operating conditions. Whether mechanical or digital, pressure switches are compact yet powerful guardians of system integrity. They may be small, but their role is huge—serving as the first line of automated defense in thousands of applications. Every secure system starts with a reliable pressure switch.