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5.3
D/A (4-20MA OUTPUT CHANNELS) CALIBRATION
The calibration can be done using the 'Auto Cal' or 'Manual Cal'.
Auto Cal
The 'Auto Cal' mode is selected in set-up 15 (and 18 for channel 2).
The analyser will automatically divert the output back to the input, measure the offset and span, and record the
calibration factors for each channel.
If either of the channels are selected to be calibrated manually, the factors will not be changed by an 'Auto Cal'.
Manual Cal
The 'Manual Cal' mode is selected in set-up 15 (and 18).
Set the 4mA calibration first and then the 20mA calibration.
1. Select 'Set 4mA Trim' in set-up 15 (or 18).
2. Return to RUN mode.
3. Measure the output on the channel to be calibrated with a digital multimeter. If the current is not exactly
4.00mA, return to set-up mode and change the 4mA calibration factor in set-up 16 (or 19).
4. Re-measure the current while back in RUN mode until the current is within 3.9 to 4.1mA.
5. Return to set-up mode and select 'Manual Cal' in set-up 15 (or 18).
Set the 20mA calibration factor.
6. Select 'Set 20mA Trim' in set-up 15 (or 18).
7. Return to RUN mode.
8. Measure the output on the channel to be calibrated with a digital multimeter. If the current is not exactly
20.00mA, return to set-up mode and change the 20mA calibration factor in set-up 17 (or 20).
9. Re-measure the current while back in RUN mode until the current is within 19.9 to 20.1mA.
10. Return to set-up mode and select 'Manual Cal' in set-up 15 (or 18).
This calibration is now saved in battery backed memory until
The factors are changed in the manual calibration
The analyser is forced into a COLD-START (see section 6.1)
The calibration mode in set-up 15 (or 18) is changed to Auto Cal and an Auto Cal is initiated.
NOTE: The 4mA or the 20mA trim mode will only be held on the output channels for 30 minutes before automatically
returning to 'Manual Cal' mode in set-up 15 (or 18).
5.4
PUMP REPLACEMENT
The reference air pump is mounted on the 1630-2 PCB in the base of the analyser. The operation of the pump is
monitored by the analyser and a "Pump Fail" alarm will be shown if a fault occurs.
To replace the pump loosen the top pump retaining screw (do not remove), remove the bottom pump retaining screw,
unplug it's electrical connector, and remove the pump.
5.5
BACK-UP BATTERY REPLACEMENT
The back-up battery is contained within the battery-like real time clock / memory module, plugged into socket M2. It is
rated for an average service life of greater than ten years. The module is not re-chargeable and should be replaced every
three years with a stored analysers with power off or every eight years with a analysers which have had the power on.
After replacing the battery, re-enter all set-up mode functions.
5.6
ELECTRONIC REPAIRS
Electronic schematics are included in Appendix 5. A competent electronic technician could perform troubleshooting
with these schematics, aided by the analyser self-diagnostic alarms. It is recommended that service be performed on a
change-over circuit board basis. A fast turn-around or replacement service is available from Novatech or accredited
service agents. Other service aids, including a test EPROM firmware package and probe or sensor input simulator is
also available.
August 2009
1635 Water Vapour Analyser
47
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