Topic: WMR200 Humidity Sensor Coating

[jonkjon]

I have read here in the past about possibly applying a fresh hygroscopic coating to the grid humidity sensor of the thgn801. I believe Polyethylene Glycol was used but i'm not sure in what manner it is applied. I know that PEG is commonly used in laxative products etc,. Does anyone know if this was applied as a paste, gel, powder? Thanks for any help with this.....

Sorry, I somehow overlooked a great post about using hair mousse gel for this....Sorry.

Jon

[jonkjon]

Just wanted to add to this that I did use a product called "Bed Head" (hair gel) that had PEG -8 listed. I cleaned the grid with alcohol until I got the lowest reading I could get and then applied one thin coating of this. As was originally mentioned, the reading jumped to its maximum (98%) until the gel began to dry. I waited until the reading settled and in my case it was reading very close to surrounding stations. I don't know how long it will last but it should at least hold me over until I can get a new sensor in.
Thanks to DanS for posting this here in the forums.....

[DanS]

Hi Jon! I did this to an older LaCrosse ws2310 that uses the same type resistance grid humidity sensor and once you get the readings set I've found the application will last and stay set for years. If you find that it's readings are not wide enough (lowest to highest) then you probably didn't add enough. In this case you just need to do the alcohol cleaning again (maybe a couple times) to get the readings back down to it's lowest. Once there use a cotton bud and swipe on a thin layer and let it dry then another thin layer and let that one dry. Do this several times. You know when each coating is dry when the humidity reading stops dropping. A thicker coating seems to absorb and disperse (breathe) moisture better.
Dan

[jonkjon]

Thanks Dan. It looks like i'll need to put a couple more coats on. My RH readings seem to be running about 10% lower than nearby stations. It also seems to be a bit sluggish. Curious though as to why i should remove the first coating though. Oh well, not a big deal, i'll give it another shot and see how it goes. Thanks again.

Jon