Additional equipment
Bourdon tube, capsule, diaphragm,
spring diaphragm pressure gauges
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In the case of a pressure surge, the overpressure safety device clos-
es immediately, in the case of a slow pressure increase, it closes
gradually. Therefore, the closing pressure to be set depends on the
values along the progression.
9.6
Pressure gauge with maximum pointer
Since Bourdon tubes have a relatively small resetting force, you
must account for their influence when installing a maximum pointer.
Maximum indicators may only be used with pressure gauge types D4
and D8 at a minimum range of 6 bar.
9.7
Electrical contacts
Electrical contacts in pressure gauges are auxiliary electrical switch-
es which open or close electrical circuits at set limit values by means
of a contact arm which is moved in accordance with the indicated
value.
See DIN 16085 for information on switching functions, require-
ments, marks, test and acceptance of electrical contacts.
If you use pressure gauges with electrical contacts to help protect
against exceeding permissible limit values, these contacts are classi-
fied as equipment with safety function (safety accessories) according
to the Pressure Equipment Directive (2014/68/EU). As per annex II
of the Pressure Equipment Directive, CE approval is required in ac-
cordance with the modules of category IV of the directive.
Sliding contact
A sliding contact is the contact of an auxiliary switch as per
EN 60947-5-1 (IEC 947-5-1). The contact is activated by the move-
ment of the gauge pointer. The movement depends on the pressure
change.
The speed at which the contact pins come closer to each other only
depends on the time the gauge pointer needs to move. The units
switch when the gauge pointer and the setting pointer are congruent.
Sliding contacts are suitable for applications which do not require
high switching power and which are not subject to vibrations. Sliding
contacts should not be used under the following conditions: high
switching frequency, corrosive environments, devices with liquid fill-
ing, hazardous areas (EX areas).
Information on the nominal operating voltage, the nominal current,
the switch rating and the switching function are shown on the dial or
the nameplate.
Standards: EN 60947-1, EN 60947-1A11, EN 60947-5-1.
