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Posted for "Tom Gourley" <tom.gourley@verizon.net>:
There are probably as many techniques and opinions on how to wire
in the shield as there are readers on the LML but the one I use is to fold the
shield back over the the outer jacket of the wire bundle, solder a wire to it,
and then put heatshrink over it.
Why bother doing that? If you are going to terminate a shield in a wire that goes into a pin, you are wasting your effort. The wire and the pin is going to have a high enough impedance at high frequencies to be rendered totally useless. There is only one way to terminate a shield: To the back-shell of a properly grounded connector. Unfortunately you are SOL if the idiot designing the avionics does not know about proper grounding.
As for single or double termination; a single terminated shield does not provide any protection whatsoever against the current induced by a nearby lightning event, as tested by the cable bundle tests in DO-150E, Section 22. With a single terminated shield, all the induced current has to travel through the wires into the pins and the devices connected to it are unlikely to survive. A single terminated shield does provide protection against ground loops created by poor wring or poorly designed avionics. The latter category, unfortunately, is a lot more common that most people realize.
Sorry that I have had to sit this discussion out due to tremendous pressure at work. On the whole, the information provided has been correct and well explained, but when people start talking about doing thing like terminating shields to pins and leaving off flyback diodes from relays/solenoids, something has to be said.
Regards,
Hamid
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