SAT III variables

[J Patrick Draine]

>I was checking some unison tunings I had done aurally tonight- most 
>of the reading seem to be fluctuating, for instance, I measure a 
>string and get -0.6, check it again and again, with varying readings 
>from -0.6 to .4.  I'm trying to play with the same force each time, 
>and measure for the same amount of time.  IF I have set them 
>properly, what other factors could be in play here?  It must be the 
>machine- it can't possibly be me! :)

Just some questions:
Are there any false beats in the strings? That could account for far 
wider variations.
Is the temperature constant? Not by a hot air duct, are you?
Are these single string measurements only, or are you comparing the 
single strings to the full (3 string) unison? If the latter, you are 
seeing the effect of string coupling (reportedly most noticeable in 
octaves 5 & 6).

Patrick