On 08/14/05 23:03 ET, LouC4 said...
I'm not an EMC engineer, but I did sleep at a
Holiday Inn ... once.
I am an EMC engineer, and try not to stay at Holiday Inn!
Any good conductor can be used for RFI shielding--ala
Faraday cage(any opening decrease effectiveness).
It must be connected to the circuit ground.
How it is connected to the ground is very important
for it to be effective.
Lou, connecting to ground is helpful, but not absolutely necessary. The Faraday cage shunts the field around the device inside the cage, even with no ground connection.
In any case, with the nice long emitter cables,
and power supply cable potentially acting as antennas
any shield is effectively nullified without addressing
these unintentional antennas. These would need
to be filtered with ferrites.
It can help with rejection of leads into and out of the cage to ground the circuit, to the correct ground. But this involves knowing which ground is correct ;-)
I didn't really want to get into a discussion here and try and determine if the noise is common mode, or differential, or some combination, so I've tried to keep things simple to start out.
I didn't think he likely had ferrites in his tool box, but if he has them and knows how to use them, I doubt he'd be here asking questions! I would use them myself, but I was trying to take an approach of using the easy things to try first.
