Sensing RF Connector Tightness Using a Grounded Plate Capacitive Structure

This paper describes a grounded plate capacitive sensing technique for monitoring mated RF connector tightness. The capacitive sensing structure and conditioning electronics are fabricated on the surface of a small polystyrene disc which is integrated into the RF connector body. A model of the electrostatic-mechanical system accurately predicts the change in capacitance as a function of the torque applied to tighten the mated connectors. Mechanical displacement in the connector (or, indirectly, axial force on the mated connector) translates to a change in the period of an oscillator drive circuit. The sensing system is measured to provide a transducer sensitivity range from 0.15 pF/N $cdot$ m at the initial connector mating force to 0.74 pF/N $cdot$ m at the high end of mating force.