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Mechanical pressure switches

Setting instructions

Setting instructions

Factory calibration of pressure switches

In view of tolerances in the characteristics of sensors and springs, and due to friction in the switching

kinematics, slight discrepancies between the setting value and the switching point are unavoidable.

The pressure switches are therefore calibrated in the factory in such a way that the setpoint

adjustment and the actual switching pressure correspond as closely as possible in the middle of

the range. Possible deviations are equally distributed on both sides.

The device is calibrated either for falling pressure (calibration at lower switching point) or for rising

pressure (calibration at higher switching point), depending on the principal application of the type

series in question.

Where the pressure switch is used at other than the basic calibration, the actual switching point

moves relative to the set switching point by the value of the average switching differential. As FEMA

pressure switches have very small switching differentials, the customer can ignore this where the

switching pressure is set only roughly. If a very precise switching point is needed, this must be

calibrated and checked in accordance with normal practice using a pressure gauge.

1. Calibration at lower switching point

2. Calibration at upper switching point

Setpoint xS corresponds to the lower switching

Setpoint xS corresponds to the upper switching

point, the upper switching point xO is higher

point, the lower switching point xU is lower

by the amount of the switching differential xd.

by the amount of the switching differential xd.

The chosen calibration type is indicated in the technical data for the relevant type series.

Setting switching pressures

Prior to adjustment, the securing pin above the scale must be loosened by not more than 2 turns and

retightened after setting. The switching pressure is set via the spindle. The set switching pressure is

shown by the scale.

To set the switching points accurately it is necessary to use a pressure gauge.

Changing the switching differential (only for switching device with suffix "V", ZF203)

By means of setscrew within the spindle. The lower switching point is not changed by the

differential adjustment; only the upper switching point is shifted by the differential. One turn of

the differential screw changes the switching differential by about 1/4 of the total differential range.

The switching differential is the hysteresis, i.e. the difference in pressure between the switching

point and the reset point.

Lead sealing of setting spindle (for plug connection housing 200 only)

The setting spindle for setting the desired value and switching differential can be covered and

sealed with sealing parts available as accessories (type designation: P2) consisting of a seal plate

and capstan screw. The sealing parts may be fitted subsequently. The painted calibration screws

are likewise covered.

Clockwise:

lower switching

pressure

Anticlockwise:

higher switching

pressure

Clockwise:

greater diffe-

rence

Anticlockwise:

smaller diffe-

rence

Direction of action of setting

spindle

With pressure switches from

the DWAMV and DWR...-203

series, the direction of action of

the differential screw is

reversed.