Either one, two or all four resistors can be strain gauges and the bridges are respectively called quarter-bridge, half-bridge or full-bridge Wheatstone bridge circuits. Pictured here are ...

We have a video on a teardown of a weight scale for you to watch, where we teach you how the strain gauges are arranged in an unusual bridge circuit. Finally, we teach you about how touch screens used ...

Even placing a proper strain gauge on the PCB had limitations. His new design uses a bridge design to make the change in the gauges usefully large. You can see a video of the project below.