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Low Cost Piezopolymer Accelerometer

IP.com Disclosure Number: IPCOM000119837D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 91K

Publishing Venue

IBM

Related People

Lee, C: AUTHOR [+3]

Abstract

Disclosed is a low cost accelerometer which uses piezoelectric polymers, e.g., polyvinylidene fluoride (PVF2), vinylidene fluoride co- polymer (VF2/VF3), as its sensing element. Because of the configuration developed, this piezopolymer accelerometer permits several important accelerometer design factors such as source capacitance, electromagnetic interference, transverse sensitivity and strain sensitivity to be satisfied simultaneously and inexpensively.

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Low Cost Piezopolymer Accelerometer

      Disclosed is a low cost accelerometer which uses
piezoelectric polymers, e.g., polyvinylidene fluoride (PVF2),
vinylidene fluoride co- polymer (VF2/VF3), as its sensing element.
Because of the configuration developed, this piezopolymer
accelerometer permits several important accelerometer design factors
such as source capacitance, electromagnetic interference, transverse
sensitivity and strain sensitivity to be satisfied simultaneously and
inexpensively.

      Because piezopolymers typically possess small capacitance and
are sensitive to electromagnetic interference, these materials in the
past have not been seriously used to develop accelerometers.
However, properties such as flexibility, softness, ruggedness,
chemical inertness, light weight and high damping factor which
characterize piezopolymers indicate that, if a way can be found to
bypass the small capacitance and electromagnetic interference effects
mentioned above, piezopolymer accelerometers can be realized.

      One of the preferred embodiments of the piezoelectric polymer
sensor element is shown in the figure.  By connecting this sensor
element to an interfacing circuit as shown in the figure,
electromagnetic interference shielding is automatically established
since the outer electrode is connected to the electric ground of the
interfacing circuit. The outer electrode can be made to be slightly
larger than the inner electrode to futher enhance the electromagnetic
interference shielding effect.  A screen-printed silver electrode is
adopted so that the folded piezopolymer still has connected
electrodes.  One thing that should be noted is that the polarity of
the accelerometer can be determined by the relative directions of the
folding and the polarity of the original piezoelectric film.

      It is clear from the figure that the piezopolymer source
capacitance and the value of the resistor Rb determine the low corner
frequency of the accelerometer cr...