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Kurt Schulz
07-22-1998, 12:24 PM
Thank you to all who responded to my inquiry re: TekScan equipment
The responses are included below.

Kurt

Look for a paper which Tim Eng and I presented at the Symposium on Functional
Footwear in Tokyo last summer. You should be able to find the abstracts or
documents through the ISB web page. There are a number of issues which you
will account for - or at least acknowledge. But the FScan system, or the
PEDAR system, will allow you to have greater room for the subject to move.
Good luck.
Sincerely,
Jon Fewster
NIKE Sport Research Lab

Just a small input: The Tekscan system is resistive measuring
technology.
The only commercially available piezoelectric technology used in
biomechanics are our force plates.
Best Regards
Christian Calame

Greetings:
Actually, the TekScan is not piezoelectric; Kistler force platforms use 3
component, piezoelectric load cells that require very expensive,
capacitance isolated cabling, and a charge amplifier for recording.
Tekscan has patented a piezoRESISTIVE polymer ink that when used with
photolithographic techniques, allows a relatively high spatial density of
pressure sensitive cells to be arranged at the intersection of an
addressable row, column matrix. Its actually the resistance of each cell
that changes with a change in local pressure, not a change in the
piezoelectric effect.
The benefit of Tekscan is the pressure distribution pattern that can be
recorded. To obtain peak force as a function of time, all non-zero cell
magnitudes (pressures) are summed, and multiplied by a scaling factor and
the active cell area. This is inherently less accurate than measuring
total vertical GRF directly using a load cell, as one would do with either
a strain gage force platform (AMTI, Bertec) or a piezoelectric force
platform (Kistler). If you have no need for individual pressure
distribution, you would achieve much more accurate results using any brand
force platform; if portability is a concern, AMTI and Kistler have portable
mounting plates for their laboratory systems.
I've compared simultaneous recordings of Kistler and Tekscan's F-Scan
system, and have found that if properly calibrated, Tekscan's
non-linearities and drift can be made more manageable. Unfortunately, it
has only been published as a conference paper:
Carollo, J.J., Parekh, R., and Winchester, P.: Calibration and force
correction of the F-Scan foot pressure measurement system. RESNA '93; Las
Vegas, Proceedings, June 12-17, 1993.
If you have trouble finding it, I'd be happy to help you.
Best Regards;
-JJC

Remember that piezoelectric sensors:
1) Cannot perform a static measurement, because the electrical charge
fades off in few seconds.
2) Keramics are only sensitive in the vertical direction, but may
have some cross-talk from other directions.
3) It is very important to know the sensor density, cause you may
loose signal if the dog contacts with a bony prominence on a
non-instrumented region.
Regards.

Ruben Lafuente-Jorge
Institute of Biomechanics of Valencia
P.O. Box 199
46980-Paterna (Spain)
E-Mail: rlafuent@ibv.upv.es
Tel: (96) 1366032
Fax: (96) 1366033

Kurt S Schulz DVM, MS
Diplomate ACVS
Assistant Professor, Small Animal Orthopedics
Department of Surgical and Radiological Sciences
2112 Tupper Hall
University of California
Davis, California 95616
ph 530-752-3599
fax 530-752-6042

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