View Full Version : Re: Strain Gauge Drift in half bridge wheatstone bridge circuit

Robert Day
07-10-1998, 12:07 AM
> 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??

Since it is only the longitudinal arm that is drifting, I would
suspect thermal expansion. The bending pair would of course be
immune to this. This would be easy to check, and could be
compensated for with some completion gauges perpendicular to the
active gauges.

Rob Day.

Robert Day rob.day@nero.rph.health.wa.gov.au
Project Bioengineer ph +61 8 9224 3227
Royal Perth Hospital fax +61 8 9224 1138

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