Measurement Proportion
Ratio of the relative change in electrical resistance to the mechanical deformation of the sensing element determines the magnitude of the signal produced by a force sensor. This strain gauge sensitivity is typically expressed as a dimensionless gauge factor, where a higher value indicates a larger change in resistance for a given amount of physical stretch. Most metallic foil gauges have a factor near two, whereas semiconductor versions can reach values over one hundred.
The choice of material dictates the resolution of the final instrument and its susceptibility to noise.
Material Response
Physical properties of the alloy used in the grid define how the resistance shifts under load. In metallic gauges, the change comes primarily from the geometric alteration of the wire length and cross section. Semiconductor gauges rely instead on the piezoresistive effect, where the mobility of charge carriers changes within the crystal lattice.
While these sensors provide much higher strain gauge sensitivity, they also introduce non linearity and temperature dependence.
Thermal Drift
Fluctuations in ambient temperature alter the baseline resistance of the gauge independently of any applied load. This thermal sensitivity can be larger than the signal from the strain itself, requiring the use of compensation techniques. Self compensated gauges are manufactured with an expansion coefficient that matches the intended mounting substrate.
Installation Effect
Quality of the bond between the gauge and the test surface limits the transfer of strain to the sensing grid. Any creep or hysteresis in the adhesive layer reduces the effective strain gauge sensitivity by absorbing some of the mechanical movement. Proper surface preparation and the use of high modulus cyanoacrylate or epoxy resins are necessary to ensure a rigid connection.
The thickness of the adhesive layer must be kept to a minimum to prevent damping of the high frequency components of the load.
