The standard high-precision way to use a three-plate differential
capacitor movement transducer is a transformer ratio arm bridge, which
was invented in 1929 (British patent 323,037) by Alan Dower Blumlein.
The subsequent US patent is 2,564,390. The advantage of Blumlein's
approach is that stray capacitances are prevented from affecting the
bridge balance.

Here are some discussions:

http://books.google.com/books?id=CMz...=PA191&dq=Blum
lein+bridge&source=bl&ots=21_dAmYpM8&sig=8c_C4rOvU gRBGFhn5quNS2oluc8&hl=e
n&ei=JQvhSaLuKZ3qlQeO1djgDg&sa=X&oi=book_result&ct =result&resnum=9#PPA192
,M1 "Introduction to Instrumentation and Control"
By A. K. Ghosh, Published by PHI Learning Pvt. Ltd., 2004, ISBN
8120316266, 9788120316263, 344 pages


http://books.google.com/books?id=ys0...PA95&dq=Blumle
in+bridge&source=bl&ots=5W1GRyrYqC&sig=6OEubB1wH8e EbtGZb-fWqN4hbBg&hl=en&
ei=QxjhScw3mtaVB5S0zeAO&sa=X&oi=book_result&ct=res ult&resnum=6#PPA93,M1
Page 93.
Transducers and Instrumentation
By D. V. S. Murty
Published by PHI Learning Pvt. Ltd., 2004
ISBN 8120309537, 9788120309531
572 pages

http://books.google.com/books?id=ppi...PP24&dq=Blumle
in+bridge&source=bl&ots=MBqZIfv5Ut&sig=AEnbBRnvtSD 4DrVgrwnz-dt2BWM&hl=en&
ei=QxjhScw3mtaVB5S0zeAO&sa=X&oi=book_result&ct=res ult&resnum=9#PPA192,M1
bad scan. described advantage of transformer ratio arm bridg for
handling stray capacitance
Comprehensive Transducers for Instrumentation
By M.G. Joshi
Published by Firewall Media, 2005
ISBN 8170082161, 9788170082163



Alan Blumlein also invented stereo, and a host of other things.

http://www.doramusic.com/patentdetails.htm

Joe Gwinn