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Subject: Re: Water sensor
Date: Fri, 10 Jan 2003 15:17:52 +0100
NNTP-Posting-Date: Fri, 10 Jan 2003 15:17:53 MET
X-Received-Date: Fri, 10 Jan 2003 15:17:53 MET (news01.chello.no)
Bruce Murphy wrote:
> Can anyone share some experiences for water sensors capable of
> detecting fairly small amounts of arbitrarily-ionised water? (Small
> enough that the large-scale mechanical float techniques won't work)
> Ideally these would be as simple/cheap as possible -- one of the
> applications involves a sensor array to detect various critical water
> events for airconditioning that has been installed far too close to
> equipment I care about.
Where do you want to detect this water? In a well defined location, or
'somewhere on this floor'?
In any case, your stuff is supposed to be dry. If you need to replace a sensor
after being drowned for too long... duh.
I'd use two electrodes, one on gnd, other via a high R to V+. C across the
conductor against interference and you can directly attach it to a cmos input pin.
For a small area, two pins could suffice. For larger areas I would look into
something with bare wires in some cloth like material, if you can figure out a
way to make that.
You could then even add some salt that generates ions but doesn't attract water
If you leave everything wet for a long time you will get corrosion. But not in a
few hours, with a few microamps flowing.