Shaw SDHmini - Using the Sdhmini to Take a Moisture Reading

Connect the SDHmini. The SDHmini is not ow sensive, however, the sample
ow needs to be enough to ll the sensor head with gas eecvely, so anything
less than 1 litre/min would mean that the instrument would take too long to sele
to a stable reading. The ow should not be so high that the gas velocity could
physically damage the sensor or cause back-pressure in the sensor head, so should
not exceed approximately 10 litres/min.
3.6 Using the SDHmini to Take a Moisture Reading
The rst purpose of the SDHmini is to provide a rapid, easy and reliable means of
carrying out moisture content measurement of gases. To ensure rapid response
the sensor is kept dry by surrounding the sensor with desiccant in the head
assembly when it is not in use.
Aer purging the system to be monitored t the SDHmini sample pipe to the
sample connecon (6). Allow the gas to purge for a further two minutes with the
head down. Restrict the outlet of the SDHmini (7) by placing a nger over the
sample exhaust (9), so that the pressure of the sample lis the telescopic head.
As soon as the head is fully extended remove the nger, to prevent pressure build
up. Pull gently on the head to make sure it is fully extended. If there is not enough
pressure to li the head assembly, assist it by pulling it up, do this very slowly so
that ambient air is not drawn in through the outlet.
The sensor will respond to the moisture level present in the sampled gas. The
displayed moisture value will connue to change unl the sensor reaches
equilibrium at which point the displayed value is representave of the moisture
level in the sampled gas. When a reading has been taken and the test is nished,
push down the telescopic head fully, carefully turn o the sample ow and
disconnect the sample pipe. With the head in the down posion the desiccant will
dry the sensor, ready for the next test.
Note: It is important that the head assembly is either fully up or fully down to
keep the desiccant isolated from the ambient air so avoiding weng it. When the
instrument is not in use it should be stored with the head in the down posion.
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