Noisy and wierd signals Ag/Cl electrodes

Sp1062Sp1062 Cambridge
in Electrodes
Hi,

I have Ag/Cl electrodes attached to my helmet, i stripped the wire from the gold plated electrodes then attached it to the Ag/Cl electrodes. I can never get the impdedance to go green. I get some really wierd signals such as this, when i am not wearing the helmet:

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Can anyone tell me the right way to use or attach these electrodes with the current wiring i have. 

image

Thanks

Comments

  • Sp1062Sp1062 Cambridge
    No filter, just notch 50hz:

    image
  • Sp1062Sp1062 Cambridge
    Channel 4 seems to always output wierd signals even without any electrodes connected. Maybe its broken?

    image
  • wjcroftwjcroft Mount Shasta, CA
    With many EEG amps, you must have electrodes connected to the head (or body in ECG) to read valid signals. This is because the differential amplifiers are based on op amps that can "run away" and do weird things if not fully connected. This is especially so because the "front end" on the Ganglion is a separate Instrumentation Amplifier.

    https://www.google.com/search?q=instrumentation+amplifier

    If you want to verify a "null" result, connect all three electrodes: active, reference, bias (or + - bias) together with either paste or a saline soaked pad. This should result in an output of close to 0 microvolts. 

    Also you need to be very careful connecting wires to electrodes. With commercial electrode wires designed for these FRI combs, the choice of metals is done very deliberately to avoid "battery" type effects.


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