Mechanical Designers & Tool Makers

Is there anything like an electronic -- not necessarily digital -- dial indicator that provides acceleration as well as deflection every few milliseconds?

Better still, would be something that already divides the distance measurement by the acceleration.

Best of all would be something like a strain gage circuit.

Resistance divided by the second time derivative of resistance . . .

I bet that can be done with a capacitor or inductor or at most a single op amp.

Bret Cahill

Doing distance? How about an LVDT?

Two op amps doing differentiation on position...

Two.

No it would take a bit more than that. Division requires a log amp, which are tricky beasts.

David A. Smith

Distance is what strain is all about.

That may work. In fact, it might not take much modification to get exactly what I want.

Thanks.

The number of really simple solutions that were possible a century that are _not_ in the literature is astounding.

Bret Cahill

Well, yes; a kind of linear motor can be connected as a generator, and the output voltage is proportional to velocity. Finding acceleration from velocity is a simple one-op-amp circuit. Old CD players used such linear motors for tracking, about 2" range.

Why?

Alas, strain gages are complex, it can take five of 'em and some clever math to (for instance) find the force on a single-point tool. Torques and lateral forces all act separately, and a separate treatment is often required. The pylon of a wind tunnel is a good well documented application of strain gage metrology.

Off topic posting, in violation of this newsgroup's charter.

Isn't that a sin, in any religion?

David A. Smith