LumaSense Technologies 3434i SF6 Leak Detector - Manual (Page 135)

Chapter 12
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BE6028-14 3434i SF6 Leak Detector LumaSense Technologies A/S
Page 135 of 191
12.1 About the Installed Optical Filters
The optical filter UA0988 has been installed in the position marked
“A” of the filter carousel wheel in your Monitor. A special optical
filter, which is selective to water vapour, is always installed in
position “W”.
The optical filter has to be span calibrated with the gas it is to
measure. If this span calibration is not performed the Monitor is
unable to measure accurately.
Each filter in the carousel has to be fully calibrated before the
Monitor can perform accurate gas measurements. The practical
calibration procedure is fairly simple, it involves performing
measurements with the Monitor while various gas supplies are at-
tached to its air-inlet.
A full calibration of the water-vapour filter SB 0527 involves:
· Zero-point calibration (using a zero-gas * )
· Span calibration (using a known concentration of water vapour)
A full calibration of the optical filter in position “A” involves:
· Zero-point calibration (using a zero-gas*)
· Humidity-interference calibration (using water-vapour)
· Span calibration (using a known concentration of the gas ( SF6)
this filter is to measure)
The following sections explain what a calibration is and why it is
necessary. Some of the expressions used in this chapter are also
explained, to help you understand the process.
* A zero-gas is a gas which does not absorb infra-red light e.g. pure Nitrogen.