How to Select the Adjustable Range of a Pressure Switch

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The adjustable range of a pressure switch is also known as the working range of the switch. It is the pressure range a switch may see under normal working conditions.

In the process of adjusting a pressure switch, accuracy and the service life could be compromised. Efforts should therefore be made when adjusting a pressure switch to ensure that the desired accuracy can be achieved while at the same time ensuring that the switch lasts long by choosing the right adjustable or working range of the pressure switch.

For the greatest accuracy, the set point of the pressure switch should be adjusted such that the set point fall in the upper 65% of the adjustable range. For a long service life, the switch set point should be adjusted to fall in the lower 65% of the adjustable range. 

Adjustable Range of a Pressure Switch

The best combination of accuracy and long service life lies in the middle 30% of the adjustable range as shown above. This rule applies to diaphragm as well as bourdon tube pressure switches.

As shown in the schematic diagram above depicting the various operating zones of the pressure switch, we can see that :

1. For optimum accuracy and long service life, select Zone A

2. For long service life, select Zone C

3. For accuracy, select Zone B

How to Calibrate and Adjust a Differential Pressure Switch

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Just like pressure switches, a differential pressure switch can be calibrated to a known set point. You can do a quick calibration of a differential pressure switch the same way you calibrate a pressure switch. However for more accurate calibrate, the procedure is slightly modified.

Before going through the calibration steps please read: How a Differential Pressure Switch Works

Quick Calibration Procedure for a Differential Pressure Switch

Equipment required includes:

(a) A variable pressure source

(b) A digital multimeter or continuity test lamp

(c) A test gauge

How a Differential Pressure Switch Works

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The Differential Pressure Switch just like the pressure switch is a simple electro- mechanical device that operates on the basic principles of Levers and opposing forces. They are mainly used for sensing a difference in pressure between two points in a plant or system. Three essential elements in the switch are used in various combinations to manufacture hundreds of variants of differential and pressure switches to suit a variety of industrial applications. These elements are:

Common Pressure Switch Designs and Applications

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The pressure switch is a very common device in any plant. Being an extremely important piece of control and monitoring equipment, its technology has evolved over the years. Pressure switches are used to interface pneumatic or hydraulic systems with electrical control systems by opening or closing electrical contacts in response to

How to Select a Pressure Switch

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With the prevalence of pressure switches in most industrial plants, it often becomes a challenge when there is the need to replace a bad pressure switch or to select a pressure switch for a new application.

The deciding factors in the selection of a pressure switch for use in your application depend on the requirements of the application. The following requirements should be considered to help you select the right pressure switch for your application:

Common Terms Used in Pressure Switch Applications

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Pressure switches are very popular and important in plant control and instrumentation. They are mainly used in control circuits and power circuits. This piece will discuss common terminology associated with the application of pressure and vacuum pressure switches in the industrial environment.

How to Calibrate a Pressure Switch with a Fluke Pressure Calibrator

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Owing to the fact that the pressure switch is a ubiquitous device, found regularly in every plant, the need to always calibrate the switch is always there. We have discussed how to calibrate and adjust a pressure switch in a previous post, but I do so again, this time using a Fluke pressure calibrator which is a very handy and popular device used by instrument technicians and experts.

How to Calibrate and Adjust a Pressure Switch

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Before we get down to the nitty-gritty of how to calibrate and adjust a pressure switch, let us get to understand some basic concepts with pressure switch calibration:

Setpoint:

This is the pressure at which the pressure switch is required to operate. A pressure switch may be set to operate on either a rising pressure (high level alarm) or

How a Pressure Switch Works

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What is a Pressure Switch?

This is a device designed to monitor a process pressure and provide an output when a set pressure (setpoint) is reached. A pressure switch does this by applying the process pressure to a diaphragm or piston to generate a force which is compared to that of a pre-compressed range spring.

A pressure switch is used to detect the presence of fluid pressure. Most pressure switches use a diaphragm or bellow as the sensing element. The movement of this sensing element is used to

Common Process Switches and Their Symbols in P&IDs

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A discrete sensor is one that is only able to indicate whether the measured variable is above or below a specified setpoint. Discrete sensors usually take the form of switches designed and built to “trip” when the measured quantity either exceeds or falls below a specified value. They are very useful in the field of instrumentation for control and alarming purposes.Most process switches are discrete in nature in that they indicate whether a process variable is