COSA Xentaur Xentaur XPDM - Manual (Page 8)

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4. Operating the XPDM
4.1. Sample Hook-up
4.1.1. Fittings
The XPDM can be hooked up to the sample gas using a variety of fittings, depending on
the application. The instruments’ sample ports are 1/4” VCO® female, to assure proper
seals for even the lowest dewpoint measurements.
Depending on the application and needs, we recommend the use of one of the following
methods of attachment:
•
VCO®
➜
VCO®: This method is ideal for all applications, including the use of flexible
stainless steel hoses, available optionally.
• VCO®
➜
Swagelok®: This method is suitable for all applications where rigid pipe
connections are acceptable.
• VCO®
➜
Swagelok®
➜
Barbed Hose Fitting: This method is acceptable for dew-
points above -65°C and should in all cases be used only with PTFE tubing.
4.1.2 Recommended Pipes
Stainless steel pipes should be used exclusively, for dewpoints below -65°C. Your repre-
sentative has a flexible stainless steel hose available. The length of the sample line to the
instrument should be kept as short as possible, to assure fast equilibrium. We recommend
the attachment of at least 12" long stainless steel pipe at the outlet port to avoid back flow
of ambient air when sampling at low flow rates, ask your representative for the optional
pigtail.
PTFE tubes are perfectly acceptable, and offer advantages due to their flexibility, for dew-
points above -65°C. However, PTFE tubes should be kept as short as possible.
Under no circumstances use rubber or plastic tubes, which are both, hygroscopic and per-
meable. No valid measurements can be expected when such materials are used.
4.1.3. Sample conditioning
• Pre-filters: Do not use any pre-filters for oil, particles or liquid water when measuring
dewpoints below -65°C. Pre-filters store and release water vapor, and slow down and
distort the measurement at low dewpoints.
• Pressure regulators: Do not use a pressure regulator containing any materials other
than stainless steel, for dewpoints below -65°C. To ensure the use of the right prod-
uct, use regulators provided by your sales representative.
4.2. Measuring
• Turn the unit on by pushing the Power button.
• Select the desired engineering units, using the up or down buttons.
• Take note of the indicated dewpoint while the sensor is still in dry-storage.
• Introduce the sample gas into the unit while the output port is unobstructed. Wait one
minute, for every 20°C below 0°C of expected dewpoint, to allow the interconnecting
hose or tube as well as the sample chamber to adapt to the sample dewpoint (eg. if
expecting -60°C, wait for 3 minutes).
• Block the outlet port. The small pressure build-up in the sample chamber should be
sufficient to push out the piston and move the sensor into the sample chamber. If not