Discussion:  Over the years the test article configuration has been made to conform to the 2.5 milli-ohm standard for bonding the ground plane to the enclosure wall.  This basically violated the rule to configure as installed.  We have seen approval representatives go to extreme measures to attain a 2.5 milli-ohm impedance connection from an equipment connector to the ground plane with several bond connections in the measurement path.  If the equipment chassis to ground connection is provided by the protective ground connection only, then the measurement should be an open circuit until that cable is installed.  We should NOT allow the measurement to mis-lead us into making an artificial ground connection.  The goal is to make the intentional ground connection and measure without adding other parallel paths (cable shields, etc.).  If you record a measurement without the intended connection, then you may be encountering incidental connections that are not assured in the installation.  Remember that 2.5-milli-ohms is not an equipment grounding requirement unless the installation specifies.

Article Reference ID: DYK00003

 

Posted in: Did You Know? MIL-STD-461G