[Diy_efi] DIY-WBO2 circuit now ceramic effects

[Bevan Weiss]

How can you say that silicon dioxide (Si02) is not a pizeoelectric crystal
(especially being a permanently polarized material)??
It's the basis of all oscillators in common manufacture.
A very thin slice of Si02 cut at a particular angle (AT/BT/90 etc), which
will have some natural vibration (I wouldn't try and doubt this, unless the
the device is at ~-273.6 degrees C), a circuit is built around the crystal
that will amplify the signal, invert it and then send it back.  This is the
basic process inside an oscillator.  The crystal itself can be used as the
filter, it will normally only allow a certain frequency to pass through it,
ie only a certain voltage frequency will be realised in the movement of the
crystal and thus produce a consecutive voltage.  However ofcourse, you can
also get overtone crystal oscillators which just uses an external circuit to
reduce oscillation at the fundamental frequency, and instead reinforce
oscillation at some particular overtone (~ n x fundamental; where n = 3, 5,
7, 9 (not higher that I know of)).

As for the others, some other popular piezoelectric materials are human skin
and bone (both having very low coupling efficiencies however)

----- Original Message -----
From: "Jay Wallace" <jwallace at nist.gov>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, June 26, 2002 1:28 AM
Subject: Re: [Diy_efi] DIY-WBO2 circuit now ceramic effects


> At 11:12 AM 6/25/2002 +0800, you wrote:
> >md4etal tapped away at the keyboard with:
> >
> > > > md4etal tapped away at the keyboard with:
> > > >
> > > > > piezoelectric effect???
> > > >
> > > > If the heater's driven by PWM, that's electrically nowhere near a
> > > > piezo element.
> > > >
> > > > If the vibration is severe enough, you may however be able to detect
> > > > it at the sensor's other terminals.
> >
> > > Please, think deeper here :  Ceramic resonator, piezo effect,
> > > ceramic media in the WB ........
> >
> > > you were basically making a 10K-20K microphone element with the
> > > ceramic media in the WB sensor!!
> >
> >There will always be a case of piezo effects on crystaline
> >structures exposed to physical distortion. An engine's exhaust is
> >probably not the most quiet environment on Earth.
>
>
> Snip....
>
> Wait a minute! Just because a material is ceramic (nonmetallic,
> inorganic) and crystalline does NOT mean that is displays any
> piezoelectric effect. Generally, ABO3 type compounds with a
> permanent electrical dipole, like BaTiO3 or PZT, are piezoelectrics
> but compounds like ZrO2 (oxygen sensors) SiO2 (glass) and Al2O3
> (spark plug insulators) are not.
>
> The long and short of it is that I wouldn't expect mechanical noise
> (vibration) in a zirconia sensor to produce any electrical signal
> by means of a piezoelectric effect.
>
> Jay
>
>
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