"Self tuning piano" questions

[Don A. Gilmore]

----- Original Message ----- 
From: "David M. Porritt" <dm.porritt@verizon.net>
To: <pianotech@ptg.org>
Sent: Thursday, December 25, 2003 10:18 AM
Subject: Re: "Self tuning piano" questions


> Don:
>
> You've described an interesting procedure.  How precise is the definition
of "one cycle" in this system?  It would seem that the start and stop timing
of one cycle would be the most critical one.
>
> Have you compared the frequency data derived in this way to data from
other measurement systems?
>
> dave
>
>
> __________________________________________
> David M. Porritt, RPT
> Meadows School of the Arts
> Southern Methodist University
> Dallas, TX 75275

Hi David:

Actually it is extremely accurate.  You can do things with electronics, even
on a simple level, that are incredible.

The one-shot counter works on the priciple that once it is triggered it
turns its output "on" at the first low-to-high transition of the square
wave.  Then it waits for the next low-to-high transition to turn it "off"
(it's counting to "one").  The reaction time is in a few nanoseconds and the
trigger pulse to start the process can be at any time since it waits to
start the pulse until the first low-to-high.

When testing the system I set it up so that a single string sustains, the
process is triggered and the counter number is sent from the processor to my
laptop comuputer every half-second or so and is displayed on the screen.  So
I get a number that refreshes twice a second.  It will only fluctuate by one
or two at A-440 (much less than a cent).

Actually I don't really care whether it matches a strobe tuner in actual
frequency since it will be tuned by hand.  As long as I tune it with the
same method I stored with, it will match the factory tuning exactly.  The
actual values are determned by the tech's ear and are immaterial.

Don A. Gilmore
Mechanical Engineer
Kansas City