LumaSense Technologies 3434i SF6 Leak Detector User Manual
Page 170
Chapter 12
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BE6028-14
3434i SF6 Leak Detector
LumaSense Technologies A/S
Page 170 of 191
12.9.2 Performing a Zero-point Calibration of the Water-
vapour Filter
As explained in the previous section, a zero-point calibration of the
water-vapour filter has to be done together with the zero-point
calibration of the other installed optical filters. The latter task has
been fully described in
. It is worth-while to emphasise
again that it is vitally important to use perfectly dry zero-gas (that
is, zero-gas which contains 0% water-vapour) during this calibration.
Note that during the zero-point calibration of filter “A” (task 1,
shown below), and during the combined zero-point calibration of
filter “A” and the water-vapour filter (task 2, shown below), a zero-
gas supply is attached to the air-inlet of the Monitor. The Monitor
measures the signal in the cell using the water-vapour filter and the
other installed optical filter. Signals measured with filter “A” enable
the concentration offset factors for filter “A” to be stored in the
filter bank which is active during calibration. However, the signal
measured with the water-vapour filter is used differently:
In Task 1:
The signal measured with the water-vapour filter is used to
compensate all measured signals for any interference caused by the
presence of any residual water-vapour in the zero-gas supply.
In Task 2:
The signal measured with the water-vapour filter is used to update
the concentration offset factor for the water-vapour filter. This
means that the signals measured with filter “A” be compensated for
the presence of any water vapour present. This is why it is vitally
important to use perfectly dry zero-gas during this task.
Please refer to
for details about how to perform a
zero-point calibration task.
12.9.3 Setting-up a Span Calibration of the Water-vapour
Filter
Remember that span calibration of the water-vapour filter is only
necessary if you wish to measure the absolute concentration of water
vapour in air samples. If the water-vapour filter is not span
calibrated you will not be able to measure the concentration of water
vapour in gas samples during a monitoring task.
Before the water-vapour filter can be span calibrated, it has to be
zero-point calibrated, that is, a concentration offset factor for the