Answer / sam

a Pressure switch is just a small diaphragm that moves as
the pressure increases. This diaphragm is pushing a small
pin upwards and the pin is pushing a micro switch to close.
Obviously if the pressure decreases again, the pin goes down
and the switch will open again. So based on this information
it is easy to see that you just need to supply pressure to
this diaphragm with a hand pump, put your multimeter on the
switch contact in order to see when the switch open or
closes and and make the adjustment on the switch until it
switches at the point where you need it to switch. The
adjustment is normally in the form of a spring.
Increasing or decreasing the tension on this spring will
change how high or low pressure is needed to move the diaphragm.
The only thing that you need to remember when working on
pressure switches, is that if you want to calibrate the
switch as a pressure switch low you need to pump the switch
up higher than your required switching point and then
decreases the pressure slowly until the switch changes
state. The same if you want to use it as a pressure switch
high, you then need to start with a low pressure and
increase your pressure slowly until the switch changes state.
Good luck

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