These small variations are one of the main problems of
strain gauges. Other problems are related to their unwanted
resistance variations due to temperature. In order to minimize
these effects, Wheatstone bridges are used to measure electrical
resistance and impedance with very small variations [3]. The
measurement is indirect by the detection of the differential
voltage in the center of the bridge. The circuit actually converts
resistance variation into voltage variation and eliminates the
offset voltage that naturally appears in a voltage divider, a
simple resistance-to-voltage converter.