To replace or regenerate the desiccant
Remove the indicator plug from the SPN1, using a 24mm A/F spanner, or
a wide flat-blade screwdriver. Unscrew the canister from the plug and
replace it with a fresh one. Check the O-ring seal in the indicator plug is in
good condition. Smear a very small amount of silicone grease on the O-
ring to improve its sealing when you reinstall it. Fresh desiccant canisters
are available from Delta-T.
The desiccant canister can be regenerated by heating. Heat the canister
in a ventilated oven (not a microwave) for four hours at about 100ºC. Allow
it to cool down away from moisture before reinstalling it.
Old desiccant can slowly lose its capacity (due to pollutants which bind
permanently). To check it, weigh before and after drying. Saturated Si gel
can carry 25% of its weight as water, so the 6gm in the canister should
lose up to 1.25 gm if it dries from saturation, or ~0.6 gm drying from 50%.
If in doubt, replace with a fresh canister.
Make sure no dust or moisture gets into the SPN1 while the plug is
unscrewed.
Maintaining the dome
Air pollution and residues in rain and snow can make the dome quite dirty.
A clean dome is essential to maintain the accuracy of the SPN1.
The dome is made of borosilicate glass. Clean it when necessary with a
damp cloth moistened with mild detergent or isopropyl alcohol.
Treatment with a water-repellent coating such a “RainX” can reduce the
amount of water and dirt on the dome. These are often sold for treatment
of car windows or bathroom mirrors.
Environment and moisture protection
The SPN1 is designed for long-term outdoor use, and is sealed to IP67. It
will withstand brief periods of full immersion, but should not be immersed
continuously in water.
Internal condensation will be avoided if you keep the desiccant fresh.
Use the sealing caps supplied to protect any connectors you are not using
from water and dust.
The SPN1 is robust, but does not have a drop test rating. The glass dome
will break if you hit it. Do not drop it.
26
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Technical reference
SPN1 User Manual v1.0
