Re: Lots of noise on the CH1 of my Olimex SMT?

Hi Kris,

I looked at your screencap, and I've a few questions:
1)  was channel 1 connected to your passive electrode or to your active 
electrode?
2) what was the source of the 2 channels?
3) what was the time interval on the horizontal axis?
4) did you use the same kind of (shielded) cables on both channels?

To me it seems that the 2 channels are 180 degrees shifted in phase. I 
don't know the schematic of the active electrode
that your using, but if the source for both channels was the same, then 
I suspect that the passive electrode was on ch1
and the active on ch2 and that the active electrode was using an 
inverting opamp.

If the cables where not both shielded, it could case this effect; if 
they were both shielded, then perhaps you interchanged the connection
from the shield of ch1 with the internal wire. If I look at the spikes 
on ch1, then it's clear to me that a source of the spikes is something
that is switching very fast. It could be the refresh frequency of the 
lcd-screen itself, therefore it's important to know the time per division,
so you can try to calculate the frequency of the spikes.

Don't forget that even if even you switch off electronic equipment, that 
there can
be something inside the equipment that is still switching!! For example, 
most pc's have an internal powersupply, that can have 2 kinds
of switching in it: one for the "off" mode, that one is generating a 
little power, for example, to detect the keyboard on/off switch or the
powerswitch of the pc itself.  But also monitors do use that system. So 
switching equipment off, is not always the solution; sometimes
you can better disconnect all the equipment in the room from the mains. 
Settop boxes, modems, almost everything is using switched
powersupplies.  Hope this helps a bit.
73, Leo.



On 10/23/2012 8:37 PM, Kris wrote:
> I think the 2 channels are working, here is a screncap of what I'm getting
> (brainbay 2ch test)
>
>
> http://imageshack.us/a/img839/1604/brainwave.jpg
>
>
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