Strain Gauge Drift in half bridge wheatstone bridge circuit

[Tim Macdonald]

Dear Biomch-l'ers,

We are currently using some strain gauges in our lab. After nulling out
our bridges, we are having difficulty with drift from the zero point even
while the gauges are unstrained. We are hoping that someone may have had
similar experiences which they were able to successfully correct.

Our configuration is as follows:
We have 4 gauges spaced around the circumference of a hollow cylinder. Two
of the gauges are wired to measure bending (i.e. wired in the same arm of
the Wheatstone bridge) and the other two for longitudinal strain (i.e.
wired in opposite arms of the bridge).
The problem is only occurring on the bridge measuring longitudinal strain.
The one to measure bending is very stable. This has us puzzled. Any
thoughts??

Thank you,
Tim MacDonald

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