Ah, but that's the question, isn't it? How do you *know* there are no ground loops?
Professional equipment is often grounded, and to get around this limitation, they use differential signals. Even transformers on occasion.
Tim
Impossible. Both rods go into the same conductive soil.
None that I've ever worked in. Any additional ground rods were boded to the existing system with at least a 3" * 1/6" copper strap.
You would be in violation of the electrical code. That ground is for safety, not hum control.
-- The movie \'Deliverance\' isn\'t a documentary!
I remember some year back, we starting seeing noise problems at the Crestline central office. Not bad, but we were having trouble meeting all our specs on the carrier lines.
Eventually, we went outside and found the grounds. There were three or four of them, in dedicated boxes. It had been a dry summer, so the ground was pretty dry, and the boxes had been painted over, and this had sealed them. We opened the boxes, and 'watered' the grounds. Gave us about 10dB better noise performance in the office!
We then made it a yearly 'routine' to water the grounds, just in case.
Charlie
Are you really claiming that forcing two ground electrodes into the ground with only 1 m separation that the electrodes are at the same potential ?
Paul
Do you always have reading comprehension problems? Do you always snip out the important parts of a message before showing your ignorance?
If I had meant that, why would I have mentioned the required bonding?
Yes, both rods are 'grounded', but have some resistance between the rods. If you don't bond the multiple ground rods, a lightning strike can cause a voltage gradient high enough to destroy your equipment.
-- The movie \'Deliverance\' isn\'t a documentary!
Please be more specific.
I did copy the first part of your message verbatim, which I was replying to.
If you are referring to the end of your original message, I really do not want to bother with your regional electric code requirements.
Paul
As good as the bonding of the connector ground to your chassis. Could be problematic since aluminium oxidises instantly on exposure to oxygen. This could lead to a high resistance connection. NEVER use insulating collars on ins and outs, it's the recipe for EMC disaster.
Not at all ( presuming the in or out screen / shield is itself already well grounded.
Graham ( EMC expert since 1987 )
Why bother? you don't want to hear anything that doesn't agree with what you think you know.
Regional codes? Yeah, that's the ticket. :(
-- The movie \'Deliverance\' isn\'t a documentary!
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Aluminum is at least as conductive a zinc, and forms the faraday cage just as easily. The issue is in the holes and the conductors connected to it.
Except that many of them have painted bottom pieces that are NOT fully integrated into the top shell, so they also leak there as well, and do NOT qualify as a full Faraday cage in nearly all "cases". Hahaha.. I made a funny.
Aluminum is third in line after Silver and Copper.
It doesn't make a bit of difference though as ANY level of metallic conductor will form a proper and COMPLETE Faraday cage. All one MUST do is be sure that the connected elements, ie. covers, etc are fully electrically integrated with the elements they are attached to.
Then, any breaches in that cage have to be below a certain size, and/or have a small enclosure of integrated metal inside that trap out (and in) any noise or signal from getting in or getting out.
mikerbgr writes
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Low power stuff, like a radio or 10W guitar amp or PC, can be powered from a wall wart or internal power supply giving say 20V - ie low voltage DC. From a safety perspective, you can get away with a plastic box round this. It floats.
The *power amps* you refer to need serious volts / amps and many power supplies of this type do not fully isolate input and output, or their safety certification requires a safety-earthed enclosure because the power supply output is >42V. So these need a 3 pin mains plug, carrying the earth too.
What the other people on this thread are saying is that an earthed case does not necessarily improve your EMC immunity, and if you need an earthed enclosure, you just have to experiment to see what works best for EMC for that particular box & circuit.
-- Nemo
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