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Subject: Re: piezo voltage sense
Date: Sat, 26 Oct 2002 18:17:47 +0100
NNTP-Posting-Date: Sat, 26 Oct 2002 17:19:51 +0000 (UTC)
User-Agent: Turnpike/6.01-U ()
In message <firstname.lastname@example.org>,
>I put the acell on an oscope and get a voltage out on screen at fast hz. I do
>not know why i cannot trip at -+ 10vac using an isolator to a comparator.
Source resistance will be high and no return path for diodes . Also
will only measure vibration ie change in g not continuous.
If all this is OK then a full wave diode bridge made with low leakage
diodes with say 1M (100k?) across the piezo terminals for return. applu
a 1000pF load out of the diode bridge and drive into an op amp follower
this should provide a dc change as the cap charges up, to add a time
constant place 1M across the 1000pf cap this will also reduce swing.
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