This laboratory uses four strain gauges connected with a wheatstone bridge (resistance-bridge) to measure strain. Two gauges are bonded to the lower leaf spring; one is on the top and the other is on the bottom. Two additional gauges are mounted to the base to provide the inactive arms of the bridge circuit.
The gauges on the leaf spring each measure the same value of strain; when the tip of the beam is deflected down, the top gauge measures the positive tensile strain and the bottom gauge measures the negative compressive strain.