Measuring center pin resistance

[Stéphane Collin]

>>   Every measurement you do in a piano should be accompanied by a relative 
>> error of measurement discussion (which should be easy)
>
> I'm not sure what you mean by this.
>
> Phil Ford

Sorry for my English, Phil.  By relative error of measurement, I mean just 
this :

when you measure, say, the length of a string, you use, say, a ribon meter 
graduated every 1 mm ; so when you take the measure of a string and find 
that it is say 1000 mm long, you should rather say that it's length is for 
sure somewhere between 999.5 mm and 1000.5 mm.  1 mm is here the absolute 
error of measurement that you make (the largest difference possible between 
your reading and the actual length of the string).  Reported to a length of 
1000 mm this means a relative error (the absolute error divided by the 
nominal length) of 0.1 % ; when reported to a length of 50 mm, the same 
system of measurement induces a relative error of 2 % , which is 20 times 
more.  When using those nominal data (1000 mm or 50 mm) in a formula 
multiplicating those values, the relative error of the results is also 
multiplicated.  We should keep an eye on the time where the results have 
such large relative errors that they don't mean anything of use anymore.
In French it is called "erreur relative".  What is the word for that in 
English ?

Best regards,

Stéphane Collin.