Re: accelerometers: primary vs. practical

[John Denker <jsd@MONMOUTH.COM>]

At 08:37 AM 7/9/00 -0400, John Gastineau wrote:
>  the accelerometer sensor does not measure
> kinematic acceleration.... Instead, the accelerometer is making
> a dynamical measurement which actually depends on the second law. In my
> opinion, that doesn't disqualify this sensor for use in the Newton II
> experiment. Here's why: the measurement I described is very easy to perform,
> and takes at most ten minutes, even with multiple masses. Before performing
> the experiment, however, I would have my students explore the behavior of
> the accelerometer.
>
> It is a fairly simple matter to show, experimentally, that the accelerometer
> readings agree with the 2nd derivative of the motion detector distance
> readings

Fair enough!

It appears we agree that the logic is circular if one doesn't at some stage
use second-derivative-of-motion data.

But the points above are well taken.
  -- One need not shun the dynamical accelerometer entirely.
  -- The act of calibrating the accelerometer can be done separately from
the act(s) of using the accelerometer.

I guess it's like metrology:  There are primary standards and practical
standards.

Thanks for calling attention to the proper use of (properly validated)
secondary standards!