Kai Klaas wrote:
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Kai Klaas wrote:
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If noise can exceed signal, lock-in methode is advantegous. But here again fast switching edges are coupled into inputs (or outputs) of linear amplifiers. Again drift, unlinearity and offset is introduced and it's very very difficult to obtain a dynamic range greater than 80dB, which represents a resolution of only 13bit!


Kai,

This is just WRONG - read up about PROPER AC Bridges and not these toy constructions, and learn about resolution of parts per TRILLION, and accuracies of 20 parts per billion.(30 bit ACCURATE)

Who in their right mind would use a square wave to excite a bridge anyway ?

http://www.aslltd.co.uk/acvdc.htm

This link might be of interest.

Steve