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Zero Gas Module
The Zero Gas Module, shown inside of the dotted rectangle in Figure 1-2, is
used to provide a dry gas stream at the inlet of the analyzer. Functionally, the
Zero Gas Module is a very simple device, consisting of only three (3) dia-
phragm valves and a dryer. The diaphragm valves used in this device are UHP
grade components; all surfaces are electropolished, and the gas connections
are welded. Because of the high quality of the surfaces in these components,
residual moisture retention is minimized. Therefore, the assembly is capable of
rapidly achieving a dry condition once the zeroing cycle has been initiated.
Under normal operation of the analyzer, both DV1 and DV3 remain closed to
protect the dryer, while DV2 is open to allow the flow of sample gas into the
analyzer. When performing the zeroing operation, DV2 is closed, while both
DV1 and DV3 are open. Thus, the flow of sample gas is diverted through
the dryer, providing a Dry-Reference (<10 PPBV) for the analyzer. By provid-
ing this Dry-Reference gas as an external challenge to the analyzer, the Zero
Gas Module enables the offsets present in the system (e.g., electronic offsets,
offsets caused by pressure differences in the different flow paths, and offsets
caused by low-level outgassing of water vapor from upstream valving) to be
measured. Normally, the magnitude of these offsets is relatively small—less
than the equivalent of 0.1 PPMV. However, as the intention of the 5830 Mois-
ture Analyzer is to have a detection limit of only 0.02 PPMV, these minor effects
must be accurately determined and removed from the moisture measurement.
Zeroing the Analyzer
The Zero process is used to correct any offsets in the Sample System. By com-
paring the two (2) Zero readings (Reference and Sample) with the internally
generated "Zero" gas, any offset can be Zeroed out. This is done by measuring
the Zero offset frequency and storing it in memory. This offset is then subtract-
ed from ∆ƒ before the sample moisture concentration is calculated.
1-8 | 5830 Moisture Analyzer
AMETEK recommends performing a Zero every 24 hours for the first
month of operation. After this start-up period, the analyzer will have
dried down sufficiently to increase the Zeroing interval to one (1)
week. AMETEK recommends that the duration of the Zero cycle be set
to 120 (i.e., 2 hours).
PN 583054901, Rev YA
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