Terminal tightness: Improving the stability of a four-terminal standard resistor

The four-terminal resistance of commonly used Tinsley Type 5685A 100 Omega resistors can vary significantly depending upon how firmly the terminals are tightened. Our measurements show a resistance to change of 12 nOmega/Omega for one resistor to an extreme case of 8000 nOmega/Omega for another resistor for which the body of one current terminal could rotate relatively easily. These findings makes it necessary to exercise care when connecting and reconnecting these resistors and also necessary to develop a way of effectively detecting or better still preventing terminal body rotation.