In a message dated 27/06/02, sbartz@....... writes:

> Has anyone ever heard of using a piezoelectric transducer in a force balance
> accelerometer?  I am in the process of building one, and it seems quite 
> sensitive
> over a broad range of frequencies.
> Steve Bartz

Hi Steve,

       Piezo transducers are not well adapted to a force balance setup. They 
are basically AC capacitative devices and have a high coefficient of voltage 
versus temperature. They have a very high leakage resistance when dry, but 
this can be a limitation in humid conditions. 

       They do make quite reasonable substitutes as uncalibrated geophones 
and you can get periods of up to about 10 seconds out of them with a TL071 
opamp or similar. I can pick up a car on the main highway 1000 yds away. 
Since they respond up to well over 1 KHz, you do need to filter seriously for 
seismic applications.

       One company does produce piezo sensors for seismic use. 

       Regards,

       Chris Chapman
In a message dated 27/06/02, sbartz@....... writes:



Has an
yone ever heard of using a piezoelectric transducer in a force balance

accelerometer?  I am in the process of building one, and it seems quite sensitive

over a broad range of frequencies.

Steve Bartz




Hi Steve,



       Piezo transducers are not well adapted to a force balance setup. They are basically AC
 capacitative devices and have a high coefficient of voltage versus temperature. They have a very high leakage resistance when 
dry, but this can be a limitation in humid conditions. 



       They do make quite reasonable substitutes as uncalibrated geophones and you can get pe
riods of up to about 10 seconds out of them with a TL071 opamp or similar. I can pick up a car on the main highway 1000 yds awa
y. Since they respond up to well over 1 KHz, you do need to filter seriously for seismic applications.



       One company does produce piezo sensors for seismic use. 



       Regards,



       Chris Chapman