7
Where practical all adjustments should be made with the transmitter installed on
the process and the range and zero settings validated by measurement of the
output signal at 0 and 100% of the process pressure. Where it is not practical to
vary the process pressure to suit, an alternative pressure source may be
employed, this should be an high accuracy device such as an air driven dead
weight tester, laboratory digital pressure standard, water or mercury column.
Range & Zero adjustments
The zero should be adjusted firstly, the instrument is of the 'live zero' type
therefore for when no pressure is applied the output signal should be 4.00mA .
Once this is achieved the range potentiometer should be adjusted with the
required max. pressure applied to the instrument until the output signal is 20mA.
It is recommended that the zero be rechecked after range adjustment
Routine Maintenance
The design of these transmitters is such that no routine maintenance is required
except for periodic examination of gaskets and security of pressure and electrical
connections
.
6. FAULT FINDING
These transmitters are sensitive and accurate measuring instruments and have no
mechanical wearing or contacting parts. If installation procedures have been
followed correctly the instrument should give satisfactory operation over a long
period.
In cases of failure or poor operation following installation or in normal service
the following check list may assist in isolating the cause of any problems.
1Are the range details of the transmitter correct for the duty?
2Fully check impulse piping and wiring installation, have any leaks
developed or are there any poor electrical connections?
3Is the transmitter isolation valve (if fitted) fully in the open position?
4Is there pressure in the process and is it of the correct order?
5Is the correct power supply applied to the transmitter and is it actually
present at the transmitter terminals?
6Check the output from the transmitter at the receiving instrument.
7 If all the foregoing are found to be in order then it will be necessary to
isolate the instrument and remove it from process.
Check that no sludge or foreign matter has collected in the transmitter pressure
chamber. Any deposits can normally be seen clearly at the entrance to the
pressure housing. Do not use any tools or other pointed objects to clean inside
the chamber, this should only be done flushing with suitable solvents
Should the problems persist consult PSM Service department
on 01444 410040 or return to the factory for examination.
