[Diy_efi] DIY-WBO2 circuit now ceramic effects

[Jay Wallace]

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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