Periodic noise in Biosemi ActiveTwo system

[sridhariisc]

Hi,

We are using the Biosemi ActiveTwo 128 channel system. When doing the saltwater (one-bucket) test, we notice that there is periodic noise at 2Hz intervals, starting at 6Hz, 8Hz, 10Hz, 14Hz, 16Hz etc (for some reason 12Hz isn't as prominent).

We have tried this test in two rooms in two different wings of our building, but the results are the same. So my guess is this is something intrinsic to the hardware. Could you advice on what might be source of this noise and how we might go about correcting it? Any pointers would be appreciated. Thanks.

[Coen]

Did you use the proper window (e.g. Hanning) in your FFT routine to prevent boundary effects ?

Best regards, Coen (BioSemi)

[sridhariisc]

Thank you for the response. Yes indeed we use multitaper spectral estimation which involves multiplying the data with Slepian sequences to minimize spectral leakage. Any other possible tests we could run with the system to confirm if this is/is not a hardware issue?

[Coen]

It is not a known hardware issue, sent the AD-box for checking and service.

Best regards, Coen (BioSemi)

[odedwer]

We encounter a similar problem with our MK2 system. Was it indeed a hardware problem?