The strain gauge is only as good as the layer of adhesive under it. Bond line thickness, cure schedule and surface finish determine creep, hysteresis and zero stability far more than gauge quality does.
Surface preparation
The element is machined, degreased, then abraded with progressively finer grit to a uniform finish, typically around Ra 1.6 or better in the gauge area. Any residual machining oil or oxide produces a weak boundary layer that creeps under load. Cleanliness is checked by the water break test: a drop of clean water should spread evenly rather than bead.
Adhesive and cure
Two-part epoxy or heat-curing phenolic is used depending on the temperature range and the creep requirement. Cure pressure ensures a thin, void-free bond line, typically a few micrometres. Under-curing leaves residual solvent that migrates over months and shows up as slow zero drift in the field, long after the cell left the factory.
Why it matters to the buyer
Creep and hysteresis specifications are set by the bond line, so two cells with identical elements and gauges can differ by a factor of two. When a supplier changes adhesive or cure schedule without telling customers, the first symptom is a batch that fails creep testing at type approval even though nothing in the datasheet changed.
Kevin Huang