An Essential Guide to Understanding Pressure Switches

Pressure switches are a part of the pressure sensor category and are widely used in process industries. Hydraulic press machines, boilers, furnaces, HVAC systems, food processing industries, and pharmaceutical manufacturing machines all make extensive use of pressure switches. A pressure switch is an electronic device that gets activated with the pressure of fluids, air or gas when they reach a setpoint. So water pumps and air compression pumps are controlled by these pressure switches. Pressure switches are designed to monitor and detect pressure and notify the user about the high pressure or lost pressure. 

There are many different types of pressure sensors made to suit different industrial needs. An incorrect pressure switch can lead to damaged equipment or even result in a hazardous work injury. But to understand their basic working principle, one has to understand in detail the different parts of a pressure switch. Most pressure switches include pistons, diaphragms, lever and electrical contacts. Pressure switches are a very important component of control systems. Understanding how these switches work is thus essential to offer a relevant solution for any application. 

What does a low-pressure switch do? 

Low-pressure switches are designed to measure small fluctuations in pressure. They prevent the loss of pressure that can damage the system’s functioning. If the pressure is absent, a low-pressure switch will turn off the process and activate an alarm. Low-pressure switches are used in hydraulic and pneumatic systems, where a steady flow of pressure is required. They are also used in air conditioning and refrigeration systems, located close to the compressor on the suction side. 

What principle do they work on?  

A pressure switch is a device that is triggered by pressure to turn or switch off an electrical circuit. It is used to measure pressure in an environment in comparison to a set limit. This limit will be different depending on the type of pressure switch and its application. Here are some key components of a pressure switch that enable its function: 

• An internal diaphragm which is used to detect the pressure element. 
• A auto/off lever that activates the switch, it can look like a knob in some designs. 
• An adjustment spring is used to set the pressure points. 
• Electric contacts that allow the flow of current to pass through them. 
• Terminals to connect the external power source to contacts. 

The working principle of a pressure switch requires the active presence of pressure. The set pressure point is adjusted with a calibrated spring. When pressure enters the switch through the port it will hit the diaphragm. Depending on the set limit, if the spring tension reaches or exceeds the pressure set point, it will move the contacts to make or break the circuit. It depends on how the contacts are from open to closed in a NO switched or closed to open with NC switch. 

Read More: The Downsides of Voltage Fluctuations

What are two types of pressure switches? 

Pressure switches are widely categorized into two types: mechanical pressure switches and electronic pressure switches. Let us understand each of them in more detail. 

Mechanical pressure switch: These switches are simple and robust in design and are better for less complex tasks. It is used to monitor the pressure of liquids, air or gas in low-cost applications. Mechanical pressure switches are cost-effective and optimised for long-term use. These pressure switches convert the fluid pressure with a mechanical movement that triggers the switch contact in the device. Mechanical pressure switches have a pre-set point at the factory, so it cannot be configured. This switch is better suited to handling high voltages.

Electronic pressure switch: Electronic pressure switches are also called digital pressure switches. They have a pressure sensor or a transducer that can be configured to provide a switch output. It provides the switch with functionalities of a transmitter and simple control tasks can be performed better with these switches. In a lot of processes these days, electronic pressure switches are replacing mechanical versions. This is because an electronic pressure switch is more advantageous than a mechanical pressure switch as it offers greater accuracy and can perform multiple switching cycles. In an electronic pressure switch, the rest point can be set conveniently. The digital pressure switches also offer additional features of a digital display with push buttons so you can manually configure the outputs. 

Related Read: Pressure Switches - An Overview

Electronic pressure switches are used in applications like hydraulic presses, tire press vulcanization, refrigerant/ammonia-based cooling systems, alarms, control and pressure monitoring. Electronic switches are generally used in industrial, OEM, control, pressure monitoring and automation. It is advisable to use electronic switches in applications that demand accuracy. When compared to mechanical switches, these switches are also more durable and can sustain thousands of pressure cycles. Because they have very few moving parts within, there is less wear and tear to the diaphragm. Mechanical switches have springs, pistons and other moving parts, which can cause more wear and tear over time.