From: Sar Saloth (sarsaloth_at_yahoo.com)
Date: 2002-03-13 22:12:54
At 09:03 AM 2002-03-13 +0000, you wrote:
>Hi all,
>
>this message is mostly for Jim Meissner, but everyone is welcome to
>comment on it, that is why I am posting it here.
>
>I have uploaded a new schematic only showing the power system of the
>high resolution EEG. Please tell me what you think. Have I gone
>completely overboard with this? I am aiming for "cell-phone
>immunity" ...
>
>I estimate that the total attenuation of HF signals is around 80-
>100dB in the 100kHz-1GHz range
I will comment (ha, you knew that would happen). You can increase the
common-mode impedance by replacing your second stage pi filter with one
that includes in inductor in the ground (just like your input stage with
the beads). Even for commercial medically approved supplies, common mode
noise is a big issue, and even when they claim that the supplies meat
everything, sometimes you have to add more common-mode impedance.
If you want to see proof - sorry, I am not able to provide any. Anyway,
that is not how I work. Once you spend $300 US/hour in a notified body's
EMI lab, you will not think twice about using the shotgun effect and
over-designing anywhere you can.
p.s. yes, there are cheaper labs, but I had no control over it. We spent
about 10 hours there in one day.
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:40 BST