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Section 2: Sensor and Sampling Techniques
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inside these materials.
• Try to run pipes to the sensor upwards, so that contaminants tend to fall back into the main
line.
• Keep the length of the sample line to the sensor as short as possible.
• Use small diameter pipes (1/4” or 1/8” OD).
• Use sufficient flow rates (e.g. 1 l/min with 6 feet of 1/8” piping is adequate). The flow rate
will influence the systems’ response time.
• Do not install any devices upstream of the sensor, such as other measuring systems, flow
meters etc., which are not absolutely necessary as these are potential leak sources.
• Installation of a coalescing and / or particulate filter ahead of the sensor is desirable to prevent
any liquid or particulate contamination of the sensor.
• If filters are used upstream of the sensor, make sure these contain non-hygroscopic filter mate-
rials only. Refer to Sample Gas Filter Considerations Appendix H.
• If pressure regulators, shut off valves etc. are used upstream of the sensor, make sure these do
not contain rubber or other hygroscopic materials.
2.4 Mechanical Installation
The sensor probe has two thread sizes for mounting to the sample cavity where the dewpoint will
be measured, see appendix C. Various optional fittings are available for direct connection into
existing system openings, refer to appendix D. Ask your representative for a Sample Cell, if you
do not have the ability to provide an appropriate sample cavity mounting. If the ¾”x16 thread is
used then the sensor will seal against the wall of the sample cell with the provided Viton A O-ring.
If the 14mm x 1.25 spark plug thread is used then an additional Viton gasket must be installed to
provide the proper seal. Ask your representative for this gasket, it is available free of charge. To
prevent any leaks, tighten the fitting into the sample cavity, with a 1
1
/
4
” wrench, 1/8 turn past fin-
ger-tight to assure metal-to-metal contact.
The sensor can be removed from the fitting by unscrewing it. Make sure that the sensor is securely
fastened to the fitting (the tension washer should be compressed), so that it does not come loose
during use.