WM81 - Adjustable Pressure Switch

WM81 - Adjustable Pressure Switch

A a non-grounded switch that responds to a drop of air pressure below a preset level.

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WM81 - Adjustable Pressure Switch

The WM-81 is a non-grounded switch that responds to a drop of air pressure below a preset level. The WM-81 adjustable pressure switch feature an adjustment that allows the actuation setting to be modified. Designed for low-voltage, low-current applications, these non-grounded switches are frequently used to activate a warning light or buzzer when a low pressure condition exists in the vehicle’s air brake system. The WM-81 is not UL approved.

Adjustable Pressure Switch: Functionality

Adjustable pressure switches are a common measuring device used in high-performance applications. They provide reliable switching for pressure, shutdown, or control and ensure devices have enough pressure to operate effectively. An adjustable pressure switch commonly has two components: a switch contact and a pressure sensor. It works by the process pressure reaching a set pressure on its input, called the switch point, and the switch contact either allows or stops current to go through the circuit. As a result, it’s the perfect monitoring solution, controlling and notifying in various applications. 

Adjustable Pressure Switch Applications

Adjustable pressure switches are used extensively in industrial and manufacturing applications. For example, hydraulic and pneumatic pressure switches control air bellows in trucks, brake pressures in trains, industrial control of equipment such as welding machines, plastic molding injection, and even medical equipment like oxygen delivery systems. They’re also widely used in automotive settings for monitoring engine oil, transmission, and power steering. In addition, it can be used to start a pump or compressor at predetermined pressures. 

There are a few considerations to take before choosing the appropriate pressure switch for an application, such as the housing on the switch, lack of housing due to space and cost limitations, whether there’s exposure to harsh chemicals or corrosives, and if you need an explosion-proof switch to protect in a flammable environment. 

Here are a few other applications widely using adjustable pressure switches:

  • Compressors - electronic gas
  • Motor control
  • HVAC equipment
  • Pumping systems - well water 
  • Process equipment

Adjustable Pressure Switch Benefits

While different pressure switches have their own individual features, you have to bear in mind the limitations. It lets the operator be precise with their switching and reset point, giving them greater control over the engineering system. 

  • High precision for extreme accuracy
  • Long-term usability
  • Operates in hazardous environments
  • Operates in high temperatures
  • Suitable for demanding hydraulic applications such as forklifts and off-road equipment.
  • Flexible with switch point, output signal, delay time, and more.
  • Come in a variety of sizes, housing options, etc.
  • Safe & Convenient
  • Economical - lower cost and space-saving designs
  • Reliable

Adjustable Pressure Switch Types

There are two main types of adjustable pressure switches:

  • Electromechanical
  • Electronic solid-state 

Electromechanical Pressure Switch

An electromechanical pressure switch measures pressure using mechanical means, such as a piston or diaphragm. This type of switch has a preset or manually adjustable switch point and can operate without auxiliary power. It also comes with many advantages, including high reliability. In addition, it handles higher voltages than electronic solid-state pressure switches and is used in cost-effective applications that require either a low or high application switching rate. 

Electronic Solid State Pressure Switch

An electronic solid-state switch features electronic pressure sensors instead of mechanical. They have integrated logic, and many functions can be programmed into the switch, such as delay time, switch point, reset switch point, hysteresis, window function, and more. As a result, they’re highly shock and vibration resistant and offer a stable solution to many applications. In addition, it typically has a long lifespan and provides an additional analogue signal in proportion to the pressure of the application.


Are pressure switches adjustable?

All pressure switches have two operating points known as the cut-in and cut-out settings. Both of these settings can be adjusted when specific applications require it to happen, making your pressure switch adjustable. The cut-in point is for the falling pressure, and the cut-out point is for the rising pressure. 

How do you adjust an adjustable pressure switch?

The first step is to disconnect the power to the switch from the power supply. After the power is disconnected, measure and write down the distance from the exposed thread from the top of the nut to the top of the stud that you adjust in inches or mm. The adjustment for the pressure switch should be to the cut-in and cut-out settings. Once the adjustment is made to those, the differential can be a secondary adjustment. 


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