Presumed RF Interference
matthew at sorbs.net
Mon Mar 6 10:17:17 UTC 2006
Peter Dambier wrote:
> Cut the ground wire in your power cords but ground the equipment directly
> to a metal frame.
As a time-served electrician... *****DO NOT DO THIS***** - it will kill
You could try separate earth bonding of each components (ie connecting
all the chassis together via a provided grounding terminal using nice
thick copper wire), however if there is a significant earth fault even
that could be dangerous (think fire) - so get a qualified electrician to
do it - if there is a ground fault it will use the chassis and the
bonded earths as it's route to ground.
Earth faults are often easily detectable by using a digital volt meter
(Note: analog volt meters do not work for this unless there is a serious
fault). First check for induced and ungrounded 'floating' voltages (any
AC or DC voltage above 0.05v should be investigated), then if the DVM is
fused, check for any current (amps) between chassis.
If you have money to spend before investigation find out if the building
has a grounding stake and if not add one... A couple of meters of
copper stake which will be connected to either the armoring of the
supply cable (TN-S) or to the incoming return cable and installation
earth PME (TN-C-S) - likely based what someone else in this threat
said. In either type of grounding scheme the structure metal frame
could (and should) be grounded (esp if exposed) which is likely to cause
the phone RF signal drop. A faulty bonding in the structure (esp as it
is steal) can also provide for some interesting ground faults as it is
not uncommon to provide localised grounding to building frames. (In the
UK where I served my apprenticeship, we were required to provide earth
bonding to the copper plumbing system, additional bonding at every
exposed fitting - this caused a few issues when plumbers first starting
using PVC pipes)... All this said with the faults appearing with no
external power and with just UPS supply, ground faults really do not
'fit' the problem - however if a generator is used also, you are in an
IT type installation (electrical term 'IT' not 'Information Technology'
;-)) and will have to have a grounding stake on site.
Please note, I am trained from the UK - laws and regulations change from
country to country - get a local qualified/licensed sparky to do the
work or assist you.
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