GB
9. Service and maintenance
2279453 08/2009 GB/D/F
WIKA Operating Instructions Differential Pressure Transmitter DELTA-trans
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9. Service and maintenance
Always open isolating devices gently, as abrupt opening may generate sudden
pressure surges that may damage the transmitter.
The pressure transmitters require no maintenance or servicing and will give very
long service when handled and operated correctly. It may well be necessary
to check and readjust the zero point periodically. This depends on the working
conditions.
To check zero point
In general, the zero point should be checked and adjusted with the instru-
ment in the unpressurised state.
With differential pressure transmitters the zero point should be checked and
adjusted by opening the pressure equalising valve while under a static load.
The plug screw (NP), found on the top of the case, must be unscrewed to
correct the zero point of the pressure transmitter. The zero point potentiometer
can then be readjusted using a small screwdriver:
turning anticlockwise
⇒
reduces the output signal
turning clockwise
⇒
increases the output signal
To check measuring span
Checking and adjusting the measuring span is a little more complex and has
to be carried out when the pressure transmitter is under pressure, up to the
upper limit of the effective range.
A sufficiently-accurate pressure standard is necessary as a reference.
Only when it is necessary to correct the measuring span should the plug
screw (SP) in the top of the case be unscrewed, and the measuring span
potentiometer can then be readjusted using a small screwdriver:
turning anticlockwise
⇒
reduces the output signal
turning clockwise
⇒
increases the output signal
Once this has been done, the zero point must be checked again and, if neces-
sary, the zero point must be readjusted. This procedure should be repeated
until the zero point and span are calibrated.
