Measuring Devices (was: String Coupling, imp. & emp.)

[Clark]

Ric:

> I would like to know if the pick up device measures differently from > others. A microphone is most used.  I wonder what the readings would > be from a magnetic pickup, or a ceramic pickup, or a PZM?

Optical pickups, too; Robert Scott mentioned these earlier. These could
be set up as pairs to measure vertical and horizontal modes.

But you raise a question about the quality of the sensor and acquisition
devices, and what degree of accuracy is necessary might hinge upon this.
John Sankey points out the amount of noise introduced by the microphone
and soundcard he used in considering the coupling effects in a
harpsichord bridge. I understand Dr. Sanderson's standard inharmonicity
predictions were averaged from a range of instruments, and I'd guess
that these measurements were carried out with SAT/SOT.

> Of course these could be compared to "lab" instruments.  I did not
> get to see what exactly these were in the thesis Don mentions.  If
> the names or types of machines  could be gotten and the set up and
> procedures and the data collecting detailed, we could get a better
> idea for comparrison.

Aside stand-alone data acquisition units (HP, for instance), 12-, 14-,
and I think 16-bit multi-sensor units are available as PCI and NUBUS
boards, where the latter should be affordable nowadays ;) Perhaps the
accuracy provided by surplus, student-grade or low-cost devices falls
below "lab" status but certainly they might well fit the budgets of
curious technicians and help closer estimate some of these moving
targets.


Roger Jolly:

I've seen photos of two controlled key-depress devices. One is a loaded
pendulum that strikes with a piano hammer, the other is a motor-driven
cog coupled to a striker developed at Tufts to test the 'new' S&S
repetition hook. I'd love a description of the "Jolly Thumper" if it's
possible.


Clark