Metal strain gauges on membranes at large deflection

The output signal of metal strain gauges on membranes combined into a half bridge was investigated at deflections larger than three times their thickness. It was discovered that the signal reaches a maximum and then decreases with increasing deflection. When the pressure was applied in the opposite direction, the signal went through a minimum and then rose with increasing deflection. This can be interpreted as a shape transition of the membrane when deflected by more than its thickness. Besides this, the asymmetry of the signal with respect to drops in pressure in opposite directions of the membrane indicates that straining of the neutral fiber of the membrane shows a notable effect. The bridge output was also investigated with strain gauges on bi-stable membranes buckling due to compressive residual stress either up or down when no pressure difference was applied.