Measuring Connector Shielding Effectiveness During Vibration

This paper describes the equipment and technique used to measure shielding effectiveness* of threaded electrical connectors during vibration. The vibration fixture is a modified coaxial trough of which the connector is a part. The connector is mechanically loaded with a short section of cable. A known current is applied on the shield of this short cable section and across the receptacle/plug interfaces. RF leakage into the interior of the cable is determined by forming the interior wiring of the cable into a closed loop and measuring the current in this loop. The logarithmic ratio of the current in the shield to the current in the interior loop is the shielding effectiveness of the cable-connector combination. The cable shield is composed of brass convolute with a braid covering and provides, by itself, 100 dB isolation. This isolation was demonstrated by testing the shielding effectiveness (S.E.) of a base-line specimen which substituted a brass fitting for the connector. It is demonstrated that this method of testing connectors can be used to determine S.E. under vibration. The method is proposed as a standard method of qualification testing of connectors.