Large artifact during button press
Posted: Thu Apr 23, 2015 5:01 pm
Hi all,
We encountered a strange issue with our Active 2 system. When using the Biosemi response box, there is a huge low frequency artifact/ drift whenever the button is pressed. We tried 2 differend responseboxes, both produce the artifact (please find a figure attached -note the large scaling on the plot!).
Interestingly, the artifact is not visible in the acquisition software during the recording, but only offline after importing the data ino matlab (might be our particular display settings in Actiview). Also, the artifact is visible on all channels, even the ones that hadn't any electrodes connected.
Another hint on the potential issue is that the trigger returned by the button press is the same that is returned by the F keys on the keybord (316).
Could there be some sort of loop/ interaction, that could be avoided by disableing the trigger input from the (recording computer's) keyboard?
Best regards,
Ulrich
We encountered a strange issue with our Active 2 system. When using the Biosemi response box, there is a huge low frequency artifact/ drift whenever the button is pressed. We tried 2 differend responseboxes, both produce the artifact (please find a figure attached -note the large scaling on the plot!).
Interestingly, the artifact is not visible in the acquisition software during the recording, but only offline after importing the data ino matlab (might be our particular display settings in Actiview). Also, the artifact is visible on all channels, even the ones that hadn't any electrodes connected.
Another hint on the potential issue is that the trigger returned by the button press is the same that is returned by the F keys on the keybord (316).
Could there be some sort of loop/ interaction, that could be avoided by disableing the trigger input from the (recording computer's) keyboard?
Best regards,
Ulrich