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View Full Version : Force measurement over 5 orders of magnitude? (Was: Owl grippingforce)



Boris Kacmar
09-08-1994, 01:53 AM
Dear netters,

I have been following your discussion and replies regarding measurement
of an owl's grip force and ideas for applicable force transducers ideas.
Since I found this discussion and replies useful I would dare to ask
this forum some questions pertaining the force transducers as well.

Our present force measurement setup used in motor control research
(muscle force measuremts - dynamic and static) is inadequate in terms
of precision and usable range for our planned future experiments.

We would like to build a new force measurement device which could be
incorporated in the existing setup. I will need to design and build
(or procure) a transducer small in physical size with usable force range
reaching from 10E-3N to approximately 300N. Apart from the fact that this
range is not a trivial problem to solve within a simple transducer design,
we will need to measure slow static force changes (slow increase or
decrease) with resolution of 10E-3N on the prestretched muscle ( say
20N or more).
So this is the core of the problem:

How can one isolate effectively this underlying (large, static) force
and measure with high resolution the small (dynamic) force differential?

I have some ideas on paper of how to solve this thing (mechanical lever
with separately placed strain gauges, optical means, resonant frequency and
phase locked loop ) but maybe someone had already solved this problem or
can suggest some good reference to this topic. I was not able to find any
existing design or hardware to meet our requirements in the strain guage
manufacturers' literature.

I will appreciate any hints, pointers or suggestion on this. I will post
summary of responses if I receive any.

Thank you for reading this rather long posting and looking forward for
your replies.

Sincerely,

Boris Kacmar

kacmar@cns.ucalgary.ca