Kahn Easidew Plus User Manual page 15

GOOD MEASUREMENT PRACTICE
Sample Conditioning
Sample conditioning is often necessary to avoid exposure of sensitive measuring
components to liquids and other contaminants which may cause damage or affect the
accuracy over time, depending on the measurement technology.
Particulate filters are used for removing dirt, rust, scale and any other solids that may
be in a sample stream. For protection against liquids, a coalescing filter should be used.
The membrane filter is a more expensive but highly effective alternative to a coalescing
filter. It provides protection from liquid droplets, and can even stop flow to the analyzer
completely when a large slug of liquid is encountered.
Condensation and Leaks
Maintaining the temperature of the sample system tubing above the dew point of the
sample is vital to prevent condensation. Any condensation invalidates the sampling
process as it changes the water vapor content of the gas being measured. Condensed
liquid can alter the humidity elsewhere by dripping or running to other locations where
it may re-evaporate.
The integrity of all connections is also an important consideration, especially when
sampling low dew points at an elevated pressure. If a small leak occurs in a high
pressure line, gas will leak out but vortices at the leak point and a negative vapor
pressure differential will also allow water vapor to contaminate the flow.
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Easidew Plus Portable Hygrometer User's Manual
Dewpoint > T Dewpoint < T
97478 Issue 1, October 2014