This document discusses using a Wheatstone bridge circuit to measure resistance. It provides instructions on how to set up the circuit with 3 known resistors and 1 unknown resistor. When balanced, the voltmeter will read 0 and the resistance values can be used to calculate the unknown resistance. It notes that when slightly imbalanced, the voltmeter reading is directly proportional to the change in resistance, allowing it to be used as a measuring device near the balance point.