Instrumentation Controls Lab (EE2327L) Practice Exam

Four-wire (Kelvin) resistance measurement works by separating the path that supplies current from the path that senses voltage. The current is forced through the unknown resistor with dedicated current leads, while a separate pair of high-impedance sense leads measures the voltage directly across the resistor’s terminals. Because almost no current flows in the sense leads, their own voltage drop is negligible, so the measured voltage reflects only the unknown resistance. The resistance is then calculated as R = V_sense / I_source, giving high accuracy even when lead or contact resistances would otherwise skew the result. This approach is especially important for small resistances or long leads. The other options would either include the lead resistance in the measurement or offer no improvement in accuracy, so they are not correct.