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Subject: Re: Humidity sensor - peculiar behavior
References: <firstname.lastname@example.org> <3E170A5E.email@example.com> <firstname.lastname@example.org>
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Date: Sat, 04 Jan 2003 19:03:43 -0500
NNTP-Posting-Date: Sat, 04 Jan 2003 19:03:45 EST
Organization: Bell Sympatico
On Sat, 04 Jan 2003 22:28:35 GMT, James Meyer
>On Sat, 04 Jan 2003 16:25:01 GMT, Roy McCammon wroth:
>>Steve Turner wrote:
>>> quite possible that I'm doing something really stupid.....
>>are you using AC or DC excitation?
> It looks like DC to me. At least DC applied to the device. It appears
>to be some sort of integrated sensor with drive, primary sensor, and output
>conditioning built into one "chip".
> The basic mechanism of the humidity sensor looks to me to be something
>that could suffer from "polarization" if driven from a DC source. I looked at
>the Honeywell web site but couldn't see any datasheets for that particular
> Given the measured results, I would be tempted to use the device in a
>sampled mode with no power applied for most of the time and only powering up and
>reading the output at intervals. Turn it on just long enough for the output to
>stabilize at a sample rate as long as I could tolerate and store the reading
>between samples. I can't imagine a humidity sensing application that would need
>more than a sample per minute.
That is the way some electronic thermometers work . They just sample
the sensor for a few milliseconds and store and display the reading
for about one minute.
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