I was thinking of the opposite of that.  Suppose I put dielectric foam
between two conductive parallel plates.  When force is applied to the
plates, the foam will deform and cause an increase in capacitance.  The only
trick is finding foam with a coefficient of deformation and thickness that
allows for capacitance changes that are significant to the measurement
instrument. The permittivity of the foam isn't important.


-Mike


----- Original Message -----
From: "Richard Mellina" <rsillem@FLASH.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Thursday, August 15, 2002 12:07 PM
Subject: Re: [EE]: Mechanical Force Transducers


>         A cheap pressure sensor can be made from conductive foam. Sandwich
the
> conductive foam between two sheets of copper foil. Solder a wire to each
> sheet of copper. It works just like a variable resistor:  when pressure is
> applied the resistance between the two plates decreases. You will probably
> need to experiment with it to find the amount of pressure associated with
> the resistance change.
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Michael A. Powers
> Sent: Wednesday, August 14, 2002 10:25 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: [EE]: Mechanical Force Transducers
>
>
> Hello,
>
> I have an application that requires the use of a mechanical force
> transducer.  Basically, I want to know the force that one flat surface
> imparts upon another.  Does anyone know of a cheap sensor that can be
bought
> (or easily made) that is appropriate?  I saw some pressure sensors in
> Jameco's catalog, but they appeared to be gas pressure sensors and
wouldn't
> be applicable here, or would they?
>
> Thanks,
> -Mike
>
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