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From: Steve Turner
Subject: Re: Humidity sensor - peculiar behavior
References: <firstname.lastname@example.org> <3E18E6A4.C30AA912@rica.net>
X-Newsreader: Forte Agent 1.92/32.572
Date: Sun, 05 Jan 2003 05:22:30 GMT
NNTP-Posting-Date: Sun, 05 Jan 2003 05:22:30 GMT
Organization: AT&T Worldnet
John Popelish wrote:
>My guess is that the device contains a 5.9kHz internal oscillator and
>a full bridge driver (probably CMOS) and a capacitance to voltage
>converter circuit that drives the output but leaks some of the
>oscillator edge to the output. This would imply that the chip should
>have a but if bypass capacitor across the supply pins, and a low pass
>filter between the output and the follower to keep the spikes from
>causing any nonlinear effects with the opamp input.
Something odd with the last sentence above: "..should have a but if
bypass capacitor..." --clarification?
Anyway, a bypass capacitor across the supply pins would be very easy
to add. I'll try that.
> With a single
>opamp follower it is very simple to produce up to a 3 pole low pass
>voltage controlled voltage source (Sallen-Key) filter with a very
>accurate gain of 1. But just a series resistor and shunt capacitor
>before the follower may suffice.
Are you suggesting that the spiking / residual AC signal may be
responsible for the behavior I'm seeing?
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