Viewing vibrating strings - longish

[Alan W Deverell]

OK - thanks Newton - I don't have any uprights so that will not be a
problem, however, my reference to "Strobe Light" for Piano Diagnostics
was a few weeks ago:

Basically I proposed a "Piano Strobe Test Unit" that could be adjusted
to PITCH + Partials etc. so as to reveal real-time phenomena including
inharmonicity etc. with the light electronically triggered from
selected piano notes and then manually adjusted to reveal other
effects. Also, it would be very nice to SWEEP a range of frequencies
to search for or detect problem string behavior etc. I suspect that
this is a bit beyond the "Lab Strobe" which you refer to below.

I include some past posting for your information and further comment:

<snip>
Yes, I can agree that, triggering the lamp from the string fundamental
may be a beginning - but - my feeling is that searching for
inharmonicity and other important effects would perhaps require
sweeping the string under some more sophisticated control. I can't yet
envisage a simple system for measuring the fundamental and then
locking on to the partials/harmonics etc. so as to render them
visible/synchronous with the Xenon strobe lamp. I have NOT yet
explored the practicality of deploying a microprocessor/controller for
such purpose, however, I am sending a copy of this mail to a friend
(George Jones) who has CURRENT experienced in system design and
deployment of microprocessor based systems for data logging, control
and scientific analysis.

I/we really need to build a flow chart and block diagram to describe
the initial parameters which need to be measured and analysed. While
interested, I just don't have time available at the present (even
writing this mail on Saturday morning is compromising to business
needs at the present time).

Perhaps for laboratory experiments a sweep/signal/pulse generator
under software control via an IEE488 bus would begin to explore the
VISUAL effects, that I speculate, could be identified as useful in a
simple technicians diagnostic tool.

I am sure that "Strobe Lights" with sufficient intensity would be
standard equipment in any Vibration Testing Lab. I have never had
hands on experience with industrial/laboratory strobe equipment so I
am ignorant about the frequency response that can be achieved with
these.

What I have accumulated is:

1) Several HV power supplies specifically designed to drive Xenon
Lamps in Photographic Compositing Equipment (pre. Gerber Plotter and
Laser Compositing where each character was exposed to the bromide/film
following character autoselection of the master character set and
optically enlarged to achieve the correct point size etc.).
2) Xenon lamps for the same
3) Lenses for the same (perhaps not necessary for this project unless
very close up refined inspection is necessary in high treble strings
etc.)
4) A~D + D~A and DIO Cards and software for ISA PC

These items, or the appropriate ones, could be shipped to you if you
are interested in combining resources.

My supposition is, that with an appropriate transducer/microphone and
sweep generator, there would be sufficient intensity from these lamps
to prove basic functionality. Development of a more versatile
experimental system, based upon the A/D~D/A PC Card could then be
undertaken to explore the utility of a stand-alone strobe test unit
suitable for Technicians.

As you will appreciate, to do this professionally / commercially is
already sounding pretty expensive, let alone the costs of writing up a
formal design specification, explore the market, do the design, make
some pre-production prototypes, do field trials, re-design as
appropriate etc. etc.

It's beginning to sound like a US$50,000 project even assuming the
cheap costs of start-up hardware.

It will be interesting to see just what interest there is to my
initial posting to Piano-Tech forum.

AlanD (going for a coffee break - I will re-read your comments later)
<SNIP>


>-----Original Message-----
>From: owner-pianotech@ptg.org
>[mailto:owner-pianotech@ptg.org]On Behalf
>Of Newton Hunt
>Sent: Wednesday, August 26, 1998 9:41 AM
>To: pianotech@ptg.org
>Subject: Re: Viewing vibrating strings in front of monitor
>
>
>Allen, take a tube home and then tune a note or two enough
>off to make
>things visible.  You can try G or G# in the second octave.  A grand
>would be best.  AN upright might get you in the back.
>
>If you needed one there are variable strobes available from Science
>supply houses.  Often used in physic class, etc.
>
>        Newton
>        nhunt@jagat.com
>
>