Selection criteria
10
Bourdon tube, capsule, diaphragm, spring diaphragm pressure gauges
the system is high-resistance (approx. 7000 Ohm), the current input
is then < 1 mA.
The difference in the current input is used to control a switching am-
plifier. This amplifier converts the input signal into a binary output
signal. Therefore, the switching function of an inductive contact is not
only determined by the inductive contact itself, but also by the
switching amplifier.
3.2
Measuring principle capsule type pressure gauge
Capsule membranes consist of circular corrugated diaphragms
sealed into a single unit. Pressure is applied in the centre and acts
on the inside of the diaphragms. The resulting deformation is propor-
tional to the pressure.
3.3
Measuring principle diaphragm pressure gauge
Diaphragm pressure gauges use circular corrugated diaphragms.
The pressure to be measured is applied at one side. The deflection
of the diaphragm is proportional to the pressure.
3.4
Measuring principle spring diaphragm pressure gauge (dif-
ferential pressure)
The pressures act on two pressure chambers separated by an elas-
tic diaphragm. If there are different pressures in the chambers, the
diaphragm is axially displaced against a compression spring. This is
transmitted to the movement by means of a rod. The differential
pressure is directly indicated by a pointer. The diaphragm is held by
a metallic support which results in an overpressure safety of up to
25 bar at both sides.
4
Selection criteria
WARNING
Injury and damage to the pressure gauge due to unsuitable
pressure gauges
Only use pressure gauges or safety pressure gauges which are
suitable for the actual operating conditions (measuring range,
ambient conditions, materials, over-pressure safety ...).
Verify compliance with all applicable directives, guidelines and
safety requirements as well as the selection criteria (safety as-
pects) as per EN 837-2 in your specific application.
