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Force sensors (2)



Rick wrote
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I suspect the air-bag sensors really measure acceleration (negative)--a
tutorial on such would be useful (anyone?), but I would think that it is
'stretching' it a bit to say that a simple spring scale measures
acceleration :-)
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Regarding springs scales:

a) first, kudos on the pun :-))

b) Do you really think its stretching the point. When you use a spring
scale to measure a force the procedure is as follows:

1) You put the spring in equilibrium. This is the step where you measure
the acceleration. You must measure the acceleration to be zero in order to
know that the spring is in equilibrium.

2) Once its in equilibrium then you measure the elongation of the spring and
read the force off the scale.

Before you read the force you had to measure the acceleration. And its in
this sense that I mean that the device really works by measuring
accleration. I think that this is how we basically make all measurements of
force, by first measuring accelerations and then making inferences. (for
the moment lets confine the discussion to spring scales as force sensors,
and then later talk about other force sensors; I want to establish agreement
or disagreement with what I say above).

Joel