B
Bill Sloman
There's a good book on the subject - H.K.P.Neubert's "Instrument
Transducers" .
It's been out of print for a long time - the second edition was
published in 1975 - but you can still buy it second hand
http://www.amazon.com/gp/offer-listing/0198563205/ref=dp_olp_0?ie=UTF8&condition=all
The first edition was enthusiastic about AC excitation of strain
gauges and resistance thermometer, in part because the Blumlein bridge
gives more sensitivity than the Wheatstone bridge
http://books.google.nl/books?id=g87...dir_esc=y#v=onepage&q=Blumlein bridge&f=false
http://www.g3ynh.info/zdocs/refs/Blumlein/BritPat323037.html
As Rayner and Kibble point out in "Coaxial AC Bridges"
http://www.amazon.com/Coaxial-AC-Bridges-B-Kibble/dp/0852743890
- also out of print - the impedances of the arms of centre-tapped 1:1
transformer winding made with twisted pair can - with care - be equal
to about one part per billion, and dissipate quite a lot less heat
than their resistive equivalent. Ratio transformers - made with
twisted bundles of wire, rather than just twisted pair - only get to
about one part in ten million, but standards laboratories love them.
AC excited bridges are more complicated than their DC equivalents, but
the complication buys you quite significant performance advantages,
and you could pack it all into a couple of square inches of board
space, even with through hole parts.
Transducers" .
It's been out of print for a long time - the second edition was
published in 1975 - but you can still buy it second hand
http://www.amazon.com/gp/offer-listing/0198563205/ref=dp_olp_0?ie=UTF8&condition=all
The first edition was enthusiastic about AC excitation of strain
gauges and resistance thermometer, in part because the Blumlein bridge
gives more sensitivity than the Wheatstone bridge
http://books.google.nl/books?id=g87...dir_esc=y#v=onepage&q=Blumlein bridge&f=false
http://www.g3ynh.info/zdocs/refs/Blumlein/BritPat323037.html
As Rayner and Kibble point out in "Coaxial AC Bridges"
http://www.amazon.com/Coaxial-AC-Bridges-B-Kibble/dp/0852743890
- also out of print - the impedances of the arms of centre-tapped 1:1
transformer winding made with twisted pair can - with care - be equal
to about one part per billion, and dissipate quite a lot less heat
than their resistive equivalent. Ratio transformers - made with
twisted bundles of wire, rather than just twisted pair - only get to
about one part in ten million, but standards laboratories love them.
AC excited bridges are more complicated than their DC equivalents, but
the complication buys you quite significant performance advantages,
and you could pack it all into a couple of square inches of board
space, even with through hole parts.