Measuring moisture in residential environment

Hi all,

A question for those knowledgeable in this area... if I was looking to measure humidity in a residential setting, what would be the best type of sensor to use? I've done basic reading on the various types, but I'd like to hear opinions from folks who really know this topic and what's out there, practical application, etc.

Ideally, this sensor would identify undesirably high humidity conditions in a normal household environment, would probably be replaced rather than recalibrated once installed, and would be sufficiently accurate to prevent any serious likelihood of false positives.

Cost, size, and reliability are of particular interest.

Anyone have any thoughts on this topic? I would greatly appreciate any input. If this would be better posted in a different newsgroup, please let me know.

Thanks!

- Chris

Reply to
Chris Brown
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"Chris Brown" wrote in news:G7ydnasvBJYzgzHbnZ2dnUVZ snipped-for-privacy@comcast.com:

Looks light the right choice of group to me..

If improvisation and cheapness are ok, you could try the resistance of paper. Crude I know, but workable, as paper is usually slightly acidic and should change substantially with humidity. Medium term repeatability will be good too, and long term repeatability could be calibrated with a portable meter, and adjustment made to a preset pot. One advantage to this crude device is that it will respond rapidly to changing humidity, and its resistance could range widely enough to make it easy to avoid false alarms.

Reply to
Lostgallifreyan

You could research using human hair as a sensor.

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Reply to
clifto

I'm no humidity expert, in fact I'm all wet! Here's a sensor you can buy from digikey for about $10:

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Reply to
Tolstoy

"Chris Brown" wrote in news:G7ydnasvBJYzgzHbnZ2dnUVZ snipped-for-privacy@comcast.com:

Are you looking for something that "trips" at a high humidity point or something linear and trip in electronics? I am thinking something like a chemical agent fixed to paper, which is optically or electronically read.

Reply to
Gary Tait

I'm thinking of something that would register elevated levels over time, or at a given point in time, without the need to trip right away when the elevation was encountered. Essentially just monitoring that humidity levels stayed within a desired range.

Thanks,

- Chris

Reply to
Chris Brown

That looks interesting. Thanks!

- Chris

Reply to
Chris Brown

Thanks for your post Lostgallifreyan.

I like your idea. For what I have in mind, though, I would eventually want to manufacture something in quantity, so though cost is certainly an object, it is not the overarching thing. In fact, not needing to visit the device to recalibrate it would rate higher on the list of objectives. This sensor would be part of a more complex assembly. I'm guessing that the challenge is not unique, though I'm not sure if there's a singular clear answer for this type of application.

Reply to
Chris Brown

"Chris Brown" wrote in news:PdadnTmy5IS7MTPbnZ2dnUVZ snipped-for-privacy@comcast.com:

Ok. :) Two other ideas came to me... One is those tiny slot counter thingers, with an LED and a photodiode. If you can find one with a bright visible red LED and nothing but the photodiode on the other side (so it's linear, near enough), you could use a piece of cobalt paper in the slot. As it changed from blue to pink with increasing humidity, it would pass more red light. The reflective types that have both LED and photodiode pointing the same way might also work.

Another thought is to make a few tiny PCB's with an interlacing of two tracks, one each side vertically with several fine extensions horizontally nearly reaching the opposite vertical. Tin these so they resist oxidising in water better than copper will, then try to find (or make) a hygroscopic paint that won't corrode the metal when it's damp. If this works, it could be by far the cheapest way to make something that will hopefully be good enough for production.

The main thing is how accountable it must be. If anything like insurance or other legal considerations matter, you'll need a sensor that has characteristics that are firmly established, and for that it will be easier to buy one ready made than to try to establish it yourself.

Reply to
Lostgallifreyan

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