How to Calibrate and Adjust the Pressure Switch Accurately

Before we get to know how to calibrate and adjust the pressure switch, let's start to understand some basic concepts of pressure switch calibration:

GE-208 Adjustable Pressure Switch

GE-208 adjustable pressure switch is a mechanical controller, made by A.YITE TECH, with CE certificate, stainless steel body  

Set point:

This is the pressure that requires the action of the pressure switch, which can be set to operate on the rising pressure (high alarm) or the falling low pressure (low alarm). Most switches are designed to operate at a "gauge" pressure set point, i.e. relative to atmospheric pressure. Some applications require an "absolute" pressure set point, that is, a pressure relative to absolute zero pressure, and an absolute pressure switch for this purpose. Ideally, the switch range should be selected so that the set point is between 25% and 75% of this range.

Dead-band or Reset:

This setting determines the amount of pressure change, required to reset the switch to normal after action. Deadband or reset or switching difference is the difference between the rising and falling pressure when the pressure switch is working. For pressure switches with fixed return differential, it is usually about 1% to 3% of the switch range. For pressure switches with adjustable return differential, it can be adjusted between about 5% and 12% of the switch range.

Pressure switches are ubiquitous devices. It's almost anywhere in your factory. But how to calibrate this simple device? The answer is here. Just follow the simple steps I outlined below.

Before calibrating the pressure switch, verify the following:

Set value of pressure switch

Return difference or deadband of switch

Also depressurize the pressure switch and isolate it from the process. If the voltage or energy exposed when opening the switch is intrinsically unsafe, follow the factory specified steps. For example, if you are in an explosive environment, use a continuously monitored gas detector to monitor the presence of explosive gases.

Digital Electronic Pressure Switches

digital Pressure switch adopts diffusion silicon sensor, 2 set point, 2 SPDT  switch, adjustable, no need calibrate ,easy adjust by press the button  

Pressure switch calibration procedure

Step 1:

Connect the pressure switch to the pressure source, e.g. by means of a manual pressure regulator and a test gauge

Step 2:

Use an ohmmeter or Digital Multimeter DMM set to a continuous range to check that the switch contacts are as shown: NO and NC.

Step 3:

Connect an Ohmmeter or DMM between the normally open contact (NO) and the common terminal (C) of the switch. The meter shall indicate "open circuit". Adjust the manual pressure regulator to increase the pressure to the set point of the pressure switch until the contact changes. The meter should now show "short circuit". Take the pressure reading and note it. This pressure is the switch set point for the "up" pressure.

Step 4:

Increase the pressure of the switch to the maximum rating. Slowly reduce the pressure of the switch until the switch is switched from off to on again. Note and record the pressure reading. This pressure is the switch setting for the "down" pressure.

Step 5:

The pressure difference between the up and down pressure settings can be obtained from the readings. This is called the "deadband" of the switch. The calculated deadband shall be equal to or less than the manufacturer's deadband.

The maximum deadband is usually specified by the manufacturer. If the maximum deadband exceeds the manufacturer's recommendations (deadband on the nameplate of the pressure switch), the pressure switch may not be used.

To calibrate the low pressure switch, perform the above steps in the following order: 1-2-4-3-5