[Eeglablist] line noise re-revisited...again

[Jeff Eriksen]

Paul,

Your understanding is correct. After amplification the analog signal is much
less susceptible to picking up any kind of noise, all else being equal.
After digitization you are in a completely different realm with different
noise sources, but nothing to worry about usually.

Mains pickup is highly dependent on the particular equipment you have, where
amplification and digitization occur, the local environment, and how
everything is grounded and interconnected.

-Jeff Eriksen
OHSU BME Dept

-----Original Message-----
From: eeglablist-bounces at sccn.ucsd.edu
[mailto:eeglablist-bounces at sccn.ucsd.edu] On Behalf Of Paul Kieffaber
Sent: Monday, February 11, 2008 8:15 AM
To: eeglablist at sccn.ucsd.edu
Subject: [Eeglablist] line noise re-revisited...again

Dear List,
I was discussing the line noise issue with someone recently and a
question came up regarding the point of introduction.  My understanding
is that most line noise is introduced to the recordings through the
cables between the electrodes and the A/D box or amplifiers.  Is there
also a risk of introducing line noise with long cables between amplifier
an the recording computer?

Our hunch is that the digital signal in those lines is not susceptible
to the introduction of noise like the analog signal between the scalp
and the amplifier.

Your thoughts and comments are appreciated.

Paul
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