Electrical-Connection-Related Stray Inductance Causing Overassessment of the Electrical Resistance Measured by Using the Two-Probe Method

Electrical resistance measurement is central to materials characterization, circuit analysis and resistance-based sensing. Resistance measurement involving the two-probe method (involving two electrical connections) is known to overassess the resistance, due to the electrode-specimen contact resistance. Resistance measurement involving the four-probe method (involving four electrical connections) is advantageous in that it essentially excludes the contact resistance at the connection-specimen interface. Nevertheless, the two-probe method is widely used, because of the simplicity of having only two connections. In the two-probe method, the current passes through the specimen and connections. The connection-related stray inductance is found in this work to cause large additional overassessment of the two-probe resistance when the electrical connection configuration entails current direction changes. The connections pertain to electrical leads and clips. The inductance increase due to a current direction change is in line with Faraday’s law. Mere constriction or spreading of the current due to the connections also increases the inductance, but it does not influence the two-probe resistance. The inductance and two-probe resistance increase with the lead length because of the connection-related inductance, not because of the negligible increase in the lead resistance. An inductance increase of ≤ 80% causes a two-probe resistance increase of ≤ 278%. The specimen in this work is aluminum. It does not need to be magnetic. The connections in this work are also not magnetic. This inductance-related source of two-probe resistance overassessment is reported here for the first time.