From: frans smith (f.smith_at_c...)
Date: 2001-06-13 14:05:02
Hi,
I understand, thanks for the explanation.
greetings.
Frans.
----- Original Message -----
From: "Joerg Hansmann" <info_at_jhansmann.de>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Wednesday, June 13, 2001 2:27 PM
Subject: Re: [buildcheapeeg] GROUNDING EEG/PC
> Hi,
>
> ----- Original Message -----
> From: frans smith <f.smith_at_c...>
> To: <buildcheapeeg_at_yahoogroups.com>
> Sent: Thursday, January 01, 1998 2:34 AM
> Subject: [buildcheapeeg] GROUNDING EEG/PC
>
>
> >Hi all,
> >Most PC-users are not aware of the fact that the pc does not
> >uses power supply like other electronical stuff (TV, radio etc).
> >The PC don''t make use of "transforming" the net-power by
> >means of a transformator. In fact, pc is directly attached to the
> >NET !!!!!
>
> PCs use primary switched power supplies. That means, that
> 230V AC is rectified, giving ca. 325V DC on a capacitor.
> The DC voltage is converted to 40kHz (and higher) AC, that
> is transformed with a HF (ferrite core) transformer which
> provides isolation between line voltage and the 5V/12V DC
> used on the mainboard.
>
> However unlike most radios and TVs (at least in Germany)
> PCs have a connection from protection earth to mainboard
> GND and all metal parts of the computer.
>
> >Should whe not warning user of rs2332 "to ground the pc"
>
> Protection earth is a good thing if the transformer isolation
> breaks down. In this case it can save your life.
>
> >Most PC users use there PC in a room where there is no
> >grounding.
>
> This is not true for Germany.
> What countries do not use PE ? (I know of Danmark, Netherlands ?)
>
> >In The netherlands grounding is only in the kitchen
> >or badroom. Grounding the PC and thus the EEG could help
> >at least to minimize the effects of accidents.
>
> The EEG must _never_ be grounded.
> In fact the EEG circuit _must_ have an isolation against all PC-signals
> (including PE or GND) that can withstand ca. 6kV according to IEC601-1.
> In the RS232EEG circuits this is done by the digital part, that transports
> RS232-data via optoisolators and by a powersupply powered by batteries
> or a DCDC converter.
>
> >Question to Joerg,
> >In electronics whe used special tranformation 220v tot 220v,
> >(i don't know the englisch name for it) so as to protect the
> >technician when working in for example an TV.
> >could the same safety-set-up be used when working with an
> >PC ?.
>
> An isolation transformer could be used for additional safety. However
> the isolation could easily be corrupted by peripheral devices like
printers
> or modems etc.
>
> Regards,
>
> Joerg
>
>
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