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When Zero-return Doesn't
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When Zero-return Doesn't |
Page 1 of 2
The electrical resistance strain gage is a
remarkably stable measurement device when properly
installed and used. With the aid of a suitable
protective
coating
, the bonded gage's resistance should remain
unchanged until a load is applied to the test
specimen. Likewise, the subsequent removal of a load
should normally result in a return of the strain gage
to its original "no-load" resistance. Any
measurable change in the installed resistance --
before or after loading -- warrants an investigation
into the cause.
Zero-Shift and Zero-Drift The resistance of a bonded gage is rarely measured precisely. More generally, the gage is connected to some form of strain gage instrumentation which is zero-balanced to "match" the installed resistance of the gage. Any subsequent change from this no-load "zero" reference point is either a reversible zero-shift, or a permanent zero-drift, in resistance. |