signal railed if ear clips are connected to ear

jessicalokejessicaloke
in Cyton
Thank you for your kind attention. 
I have an Ultracortex Mark IV connected to 8 channels which seems to be giving me a signal upon starting in the GUI. It continues to give me a signal when I put the device on my head. It continues providing a signal until I connect the ear clips to my ears.Then, the channels will become "railed".
Both ear clips are connected to SRB (upper) and bias (upper) respectively as shown in the getting started guide. What could be giving me this issue? Thank you in advanced!

Comments

  • wjcroftwjcroft Mount Shasta, CA
    Jessica, hi.

    Are all your connections to the board, using the pins CLOSEST to the board surface?

    Can you try placing the headset on your head WITH earclips, THEN starting the GUI? Don't start the GUI with the earclips off.

    You can also check wire and connector continuity (disconnected from the Cyton), using a digital ohmmeter.

    William

  • jessicalokejessicaloke
    Hello William,

    Thank you for the prompt response!

    If I first place the headset on my head with earclips, then start the GUI, all channels will be railed from the start.

    I've also checked the wires using a digital ohmmeter and it seems to be working fine. 

    Any other ideas?

    Thank you again!
    jessica
  • jessicalokejessicaloke
    edited December 2017
    With the exception of the earclips, all connections to the board are made to the pins closest to the board surface.

  • wjcroftwjcroft Mount Shasta, CA
    Your image link did not work. Microsoft Outlook URLs require an active login. Can you place on Google Drive and supply that URL?

  • wjcroftwjcroft Mount Shasta, CA
    A standard test for EEG systems, is to connect (with say clip leads or conductive material), all the channels, plus reference plus Bias. This should produce a signal very close to zero microvolts.

    It's possible you may have defective ear clips. Can you also try swapping the Bias and Reference ear clips.
  • jessicalokejessicaloke
    Here is the photograph of the board

    https://drive.google.com/open?id=1Y4TnvDpUcdCxeug5MRlAsXpGFZAbxyRG

    I’ve tried swapping the ear clips between SRB and bias but receiving the same results. However, if I plug the ear clips into different places (e.g. SRB bottom + SRB upper or SRB bottom + bias bottom) it seems to give me different results, but it would eventually become railed as well.
  • wjcroftwjcroft Mount Shasta, CA
    Did you try the clip lead test I suggested? Do you have alligator clips or it could also be done with extra header pin connector cables.
  • jessicalokejessicaloke
    I’ll try the clip lead test when I get back to the office. In the mean time, happy holidays :) hope you have a good one.
  • wjcroftwjcroft Mount Shasta, CA
    Thanks, you can just test one channel at a time by connecting it with Bias and Ref. Might reduce the number of leads you need.

    If you get the zero microvolts, that means the ADS1299 chip is working correctly. Must be an issue with electrodes, wires, connectors.
  • jessicalokejessicaloke
    I've done the clip lead test and got a number close to zero. 
    On the other hand, I've changed the SRB pin to the bottom one - next to the other electrode pins. Photo here: https://drive.google.com/open?id=1BvktqSrrucerjDeAVrZRMwOU94fX4605
    And half the electrodes seem to give me a decent signal, whereas the other half remain railed - although all have proper contact with my head.
  • wjcroftwjcroft Mount Shasta, CA
    The zero microvolts test means the ADS1299 chip and firmware are working fine. You must have an issue with your electrodes or skin contact or wire connectors, etc. Did you build and print this headset yourself? Is it possible that some of the electrode assemblies are loose, not fully conductive (with an ohmmeter) etc.?

    The SRB2 pin is the one closest to the board and is the default common reference, UNLESS you are changing settings in the GUI.

    For the electrodes that are railing, check with your ohmmeter each continuity. And try the zero microvolts test on that lead. Is there any corrosion or missing silver chloride plating on the electrodes, etc. Does the railing happen for other people than yourself? 
  • wjcroftwjcroft Mount Shasta, CA
    Since this issue seems to be related to the ear clips, be sure to do the ohmmeter check on both of them. Check the chloride plating, which should look blackish. You could also try another way of getting the reference and bias connected to the skull. Which is to use what is called the ear mastoid connection with a stick on pre-gelled electrode.


    Or instead of the pre-gelled, you could try a cup electrode with paste. But the pre-gelled uses the same silver chloride as the other headset electrodes. Which is always a good match of metal types.
  • 1927student1927student
    @wjcroft
    You keep mentioning in various posts to connect the ear clips to pins close to the boards (SRB and Bias). However, the guide on OpenBCI webpage says to connect it to the top or upper pins. Please clarify! I am also getting a railed signal for most of my electrodes in 16 channel.
    http://docs.openbci.com/Headware/01-Ultracortex-Mark-IV

  • wjcroftwjcroft Mount Shasta, CA
    If the Cyton is held in your hand with the pins on the top, then "closest to board" and "upper pins" are the same pins. The clarification is so regardless which way you look at the board, "closest" always means those pins laying flattest to the board. This is clear on the photo images shown in the tutorials.

    Did you do some of the other checks mentioned in this thread?

  • pushtheworldpushtheworld
    Please make sure to verify that there is no corrosion on the electrodes, that can lead to railed signals. Cyton for EEG has all pins on the bottom row.
  • wjcroftwjcroft Mount Shasta, CA
    edited January 2018
    By "bottom", AJ means "closest to board". "Bottom, top, upper, lower", one can see how these terms can confuse without adding another as to 'what' the direction is in reference to.

  • mf97mf97 brasil
    edited January 2018
    Hi guys.
    I am facing the same problem. 
    Im using the Cyton board and the Mark IV.
    A while back the Cyton was working fine. But now it seens like having a problem showing only railed signals on the OpenBCI Gui.
    I did already check all youve talked here

    Heres the cyton with the pin connected. 
    https://drive.google.com/open?id=1GV-jTT3UgyoYDy_p3TabpdA7fN7yG5e_

    I also tried to use just two channels but this two appears as RAILED while the others (not connected) show a value close to 0. I dont know what it means

    Please show me some away to get it right!!!

    image
  • jeyemjeyem
    @wjcroft: What 1927student is referring to are these two pictures in the assembly instructions. This is obviously misleading for many newbees.

    https://raw.githubusercontent.com/OpenBCI/Docs/master/assets/images/MarkIV/MarkIV_cyton_connects_nocover.JPG
    https://raw.githubusercontent.com/OpenBCI/Docs/master/assets/images/MarkIV/MarkIV_cyton_connects_cover.JPG


  • wjcroftwjcroft Mount Shasta, CA
    @jeyem, thanks.

    Logged the issue at,


  • pushtheworldpushtheworld
    that's a bad photo!!!!! forwarding to team on multiple fronts!
Sign In or Register to comment.

© Vanilla Keystone Theme 2026