From: Spehro Pefhany
Subject: Re: Humidity sensor - peculiar behavior
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Date: Sun, 05 Jan 2003 01:46:41 GMT
NNTP-Posting-Date: Sat, 04 Jan 2003 20:46:41 EST
On Sun, 05 Jan 2003 01:37:01 GMT, the renowned Steve Turner
>Spehro Pefhany wrote:
>>P.S. I see you've eliminated the possibility of oscillation of the
>>follower in your original post, but what about the sensor output?
>I've looked at both the sensor output and the follower output with a
>scope. The sensor output shows some noise, perhaps 10 mV p/p, plus
>very sharp spikes of about 400 mV p/p at about 5.9 KHz. The follower
>output shows a 5.9 KHz fundamental signal as well, attenuated (maybe
>50 mV p/p), full of harmonics with a decaying envelope. I don't know
>if any of this is relevant to anything. It is definitely not square
>wave and looks nothing like oscillating op amps that I've seen in the
I'd expect there to be some AC from the sensor energization (it's
a polymer type, so it "looks" like a variable capacitor).
Well, this is a 3-terminal device, and you seem to know what you
are doing humidity-wise (well, it would be nice if you had another
sensor of a different type to compare it to, just to be sure).
Next step is probably to call their support people and see what they
have to say. Maybe you have a defective one. Hard to imagine though.
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