Pressure switch calibration is necessary for industrial safety.Pressure switch needs to be calibrated to ensure their accuracy and reliability. Pressure switch bit difficult to calibrate than transmitter. In this article will look at how to properly calibrate Pressure switch.
1:- Pressure Source
2:- Accurate Gauge
3:- Micro switch contact monitoring device.
4:- For high pressure application Hand pump is more suitable.
5:-For low pressure shop air or simple regulated pressure can be used or electronic pressure source can be used.
6:- Pressure should have an accuracy of 0.25 %.
1:-Connect the pres. switch to a hand pressure regulator and test gauge.
2:- With a Multimeter, set to the continuity range to check and verify that the switch contacts indication are: NO (Normally open) Or NC (Normally close).
3:- Connect the Ohmmeter or DMM between the normally open contacts (NO) and the common terminal (C) of the switch. The meter should read ―open circuit(No)
4:-Adjust the hand pressure regulator to increase the pressure to the set point of the press. switch until the contacts change over. The meter should now read ―short circuit(NC). Note the pressure reading and write it down. This pressure is the switch set point for a ―rising pressure.
5:- Increase the pressure to the switch to its maximum rating. Slowly reduce the pressure to the switch until the switch changes over from closed to normally open again. Note and write down this pressure reading. This pressure is the switch setting for a ―falling pressure. When error found, adjust set point by screw adjustment and repeat until desired value obtained.
6:- From the readings you have taken work out the pressure difference between the rising and falling pressure settings. This is called the―dead band of the switch. The dead-band calculated should be equal to or less than the manufacturers‘dead-band. The maximum dead- band is usually stated by the manufacturer.