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From: Bruce Murphy
Subject: Re: Water sensor
Date: 12 Jan 2003 14:09:00 +0800
Organization: The University of Western Australia
X-Newsreader: Gnus v5.5/XEmacs 20.4 - "Emerald"
Tony Williams writes:
> In article ,
> Bruce Murphy wrote:
> > 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.
> How about a small PTC Thermistor, powered by a
> voltage large enough so that the temperature of
> the thermistor exceeds 100C in air. Monitor the
> current drawn for a measurement of its resistance.
> When in water the thermistor will struggle to get
> above 100C as it tries to evaporate the water off
> (540 cals/gm?). At that point its resistance will
> be stuck down at the 100C value.
While this is a cute idea, since the sensors have to be small, this
strikes me as replacing one hazard with another.
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