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Re: Tuning Forks



1) have you tried using a strobe. lamp?
2) depends on accuracy desired -- simplest is a bending beam of no mass
and a mass at the end not clamped in a vise
3) google search results in some rather interesting methods of
construction and driving of mechanical forks for gyroscopes and a shear
force sensor.

http://clifton.mech.northwestern.edu/~me381/project/02fall/Gyroscope.pdf

http://unit.aist.go.jp/photonics/q-nano/presentation/pdf/ultra.ultra90.pdf

Sci. Am. describes the modification on a tuning fork frequency std.
operated in a vacuum if my memory serves.

bc who has a tuning fork frequency std. that uses a magnetic drive
with a carbon microphone feed back detector

Roger Haar wrote:

Hi,

Here at the U of Arizona, in our junior-senior
lab, we have the students make tuning forks as an
introduction to machining metal. We measure the
fork's frequency when it is complete, with an
amplified microphone and a frequency counter. This
is quite popular activity.

But there are several questions about tuning
forks that come up:

1. Physically, how is the tuning fork bending in
its fundamental and harmonics?

2. What is the theoretical resonant frequency or
how to design a tuning fork for a desired
frequency?

3. Many of our tuning forks including several
commercially made tuning forks resonate on 5th
(or maybe 4th) harmonic. Often this harmonic is
much stronger than the fundamental, but usually
this harmonic decays faster than the fundamental
so we can eventually get a good measurement.
Is there a method of exciting a tuning fork to
avoid harmonics?

Thanks
Roger Haar