Mechanical pressure switches: How does one set the switch point?

Mechanical pressure switches are usually supplied with a factory-set switch point. Nevertheless, some users want to get this to configuration themselves, as, for instance, the pressure conditions in the application form can change. Regarding pressure switches with a measuring element in a bellows, diaphragm or piston design, the manual setting of the switch point, reset point or hysteresis (based on the model) requires a specific amount of effort. Nonetheless it?s not witchcraft. This short article explains, step-by-step, how to take action.
Users need the following equipment: a pressure source (e.g. a dead-weight tester), a control pressure gauge, a continuity tester or a control lamp as well as a tool for the adjustment screw (by the way, WIKA supplies the correct Allen key with its instruments; the standard screwdriver is sufficient for setting the hysteresis).
Setting plan view for the model PSM02 mechanical pressure switch from WIKA. The pin assignment 1 and 3 (small picture) corresponds to the switching function ?normally closed?, the assignment 2 and 3 would be for ?normally open?.
Setting of the switch point
First, screw the pressure switch in to the pressure source connection and connect its electrical connections to the continuity tester or control lamp.
Turn digital pressure gauge ราคา for the switch point in completely. This sets the switch point to the highest possible value.
Now apply the desired switching pressure to the pressure switch before control pressure gauge indicates the value.
From then on, turn the adjustment screw out until the instrument switches and the continuity tester or the control lamp reacts.
Then lower the pressure until the pressure switch switches back and then increase it again to check on the switch point. If necessary, the switch point must be corrected by turning the adjustment screw. Repeat the procedure until the desired switch point is reached.
Setting of the reset point
In some applications, the reset point is set instead of the switch point, e.g. for minimum pressure monitoring. Here the task is comparable to the switch point, but without turning in the adjustment screw.
Increase the pressure until the instrument switches.
Then lower the pressure before instrument switches back and adjust the positioning of the adjustment screw accordingly. The rule of thumb here is:
Set point < Actual value: Turn the screw out
Set point > Actual value: Turn the screw in
Setting of the hysteresis (not with all models)
To do this, first set the switch point and check the reset point (see above). Depending on reset point, the hysteresis screw is turned in or out. The switch point must then be checked, as changes to the hysteresis screw also affect the switch point.
Note
An overview of the many mechanical pressure switches along with further technical information can be found on the WIKA website. For those who have any questions, your contact will gladly assist you to.
Also read our articles
Mechanical vs. electronic pressure switches: Functionality
Mechanical vs electronic pressure switches: Application areas
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