Low-frequency noise in a one-bucket test
Posted: Wed Jul 29, 2015 12:41 pm
Hi.
I've just started working with a Biosemi EEG system we have in our lab for some time, and wanted to start from testing it, so I ran a one-bucket test for now for the external electrodes (That is, I used a bucket of water with salt, and submerged the CMS/DRL and all external electrodes in the water). Also canceled to filters as recommended. According to the user manual I should expect a flat line if everything is alright. However, what I actually got was a low-frequency drifts in all channels. Only when I turned the high-pass on-line filter on (cut-off of 6hz and maybe even less), I got the expected flat line.
What does it mean? I would be very helpfull for any help interpreting this.
Thanks,
Isaac
I've just started working with a Biosemi EEG system we have in our lab for some time, and wanted to start from testing it, so I ran a one-bucket test for now for the external electrodes (That is, I used a bucket of water with salt, and submerged the CMS/DRL and all external electrodes in the water). Also canceled to filters as recommended. According to the user manual I should expect a flat line if everything is alright. However, what I actually got was a low-frequency drifts in all channels. Only when I turned the high-pass on-line filter on (cut-off of 6hz and maybe even less), I got the expected flat line.
What does it mean? I would be very helpfull for any help interpreting this.
Thanks,
Isaac