Calibration of ETDs

[Kevin E. Ramsey]

    My God, if the accu-tuner isn't exactly on pitch all the time, what can
we believe in?
    Really folks, when we are dealing with tenths of a cent, we really ARE
splitting hairs. I checked one of our "concert" techs ( of which I are one,
but it was the other guy, ) forks recently, he had no way of calibrating
it,,, and it was four cents sharp! I admit, that's not a bad pitch, since
the piano can drop from 441 to 440 when you're pounding in unisons; but I
like to pound them in to the fork. At least then I know that my A is rock
solid. (After I've done a pitch raise, and fidgeted around for an extra
half-hour). This is only on pianos that are expected to be "pounded" in
concert after I'm done. I only do "firm" test blows on in-home instruments.
HHHHHHHMMMMMMMMm....... another topic for discussion?


Kevin E. Ramsey
ramsey@extremezone.com
----- Original Message -----
From: "Robert Scott" <rscott@wwnet.net>
To: <pianotech@ptg.org>
Sent: Saturday, January 20, 2001 3:16 PM
Subject: Re: Calibration of ETDs


> Kevin E. Ramsey wrote:
>
> >    When I first got my SAT, I calibrated my forks to be at exactly 440
when
> >at body temperature. I achieve this by tucking it between by belt and my
> >body for about two minutes. I still have one of those forks in a drawer
in
> >my dresser, as a back-up. I check it once in a blue moon. It hasn't
changed
> >by a tenth of a cent in eight years, according to my SAT, so I kinda get
the
> >impression that the SAT isn't changing either.
>
> Yes, as long as your fork is not dented or bent and is kept clean and
> used a the same temperature, it will be quite good as a standard.
> Some tests that I performed recently on a medium-grade fork showed
> that it takes 7.5 degrees Fahrenheit temperature change to make the
> fork change 1 cent.  So if you want .1 cent accuracy in a fork you
> would need .75 degree temperature control.
>
> >    I was under the impression that the SAT uses a quartz crystal, which
can
> >only oscillate at one frequency. Let me know if you think I'm wrong.
>
> A quartz crystal ocsillator can change its frequency with changes
> in temperature, battery voltage, etc., although it does not change
> nearly as much as a fork.  And I am sure that the SAT incorporates
> all the best voltage regulation and temperature compensation techniques
> to achieve stability.  But things can go wrong, so it's good to be able
> to do a check-up once in a while.
>
> -Robert Scott
>  Ypsilanti, Michigan
>
>