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{\large {\bf Comment}}\\[2mm]
Matchstick Calibrations
}}\\[7mm]
\makebox[2.5cm][l]{Author:} Bill Rae\\[2mm]
\makebox[2.5cm][l]{Date:} 2 June 1992\\[2mm]
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\noindent
Distribution: \parbox[t]{12cm}{
WNC,NMC,PVD,BRF,GJG,RAH,JSL,WDMR,GT,DLW\\
}\\[2mm]


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~ & ~ \\ \hline
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{\large {\bf Matchsticks and Gain Matching}} %\\[1cm]
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I am concerned that we have slipped into the mistake of assuming that all the
test input capacitors are matched, and hence that matchstick runs can be 
used on their own for gain matching. In fact, to do proper gain 
matching you need
to know the relative test input capacitance values. When these pre-amps were
first introduced the test input capacitances were measured at the end of runs,
but more recently this has not been happening. This is something
that need only be done once and the two values for top and bottom could
be recorded with the serial number of the pre-amp. All that is needed is the
capacitance relative to a fixed test capacitor of which we have several
from pre-charissa days. We need someone to undertake this task. 
People must note the serial number and up/down for each preamp after each 
run.\\[1mm]



 W.D.M. Rae 

2/6/92\\[2mm]


Peter Simmons adds a comment about the 7\al\ data:\\[1mm]

After correcting the gains at each end of each strip using the data from the 
matchsticks, it was found that some of the gold elastic peaks were still like:
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when plotting E vertically against P horizontally. This was caused by gain 
mismatch between the ends of the strip. To correct this it was necessary to 
multiply by a linear factor in P. This factor was introduced by spline 
fitting the elastic gold peaks. Normally this fit would only include higher 
order correction terms in P, but for badly gain matched strips, it also 
included a linear P term. \hfill $\Box $


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