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zamzald · Joined: Mar 18, 2016 Posts: 3

Hi everyone,

I'm having a lot of noise at 50 hz from electrical devices nearby, especially from a newly purchased TV that I'm planning to use as a client screen. I was wondering what I could to solve that problem? I'm using a Q-wiz from Pocket neurobics.

Will a software filter at 50 hz be enough?
Does the TV disturb any other signal than the obvious 50 hz? A manufacturer told me that performing FFT may make that clear, but I don't know much about FFT or how to perform it.
What about using some kind of transformator?

I greatly appreciate any help.

Thanks.

jarek · Joined: Oct 22, 2007 Posts: 1073

I have two large TVs in the room (which I use as monitors) and I don't observe much noise, so maybe this particular TV is not behaving as it should. Try to keep the device and electrode wires as far from it as possible.

Software filter at 50Hz can help only if the signal is not saturated with the noise. If there is too much noise in the signal nothing will help.

No, the FFT would not be useful here. Filter will work well enough and is easier to use.

If your design has bandpass filters, then you might not need to do anything else.

If not (or if you wish to see/process the signal without noise), then you could try to connect lowpass filter (for example <45Hz) and see if that makes it good.

jarek · Joined: Oct 22, 2007 Posts: 1073

Also make sure your electrodes have good connection.

zamzald · Joined: Mar 18, 2016 Posts: 3

@Jarek thanks for your response.

The training room is small, so unfortunately I can't really change the distance much.

Let me show you a video of the problem: https://www.youtube.com/watch?v=xabXOrk8zXE

jarek · Joined: Oct 22, 2007 Posts: 1073

You are not using BioEra in that video. This forum is about BioEra support.

zamzald · Joined: Mar 18, 2016 Posts: 3

Jarek, the video was recorded before I found out about Bioera. I am very glad to have found Bioera and I'm very much looking forward to moving all my designs from a VERY outdated software to this software. So please ignore the software that was used in that video. My questions are only intended to be about using my current hardware setup with Bioera.

Do you think the TV has a problem?

Is there any way I can check be sure if the signal is too saturated using Bioera (or some other tool)?

What do you think I should do?

jarek · Joined: Oct 22, 2007 Posts: 1073

I have little experience with high interference, I usually try to make sure this is not the case before I start a session (this means moving away from all devices).

You can look at (your noisy) signal amplitude and compare it with maximum possible amplitude (if you don't know it, you can watch it by touching the electrodes with your hand). Your noisy signal should be well below that line, I would say less than half should be fine (just an educated guess).

Also (as I already mentioned) make sure your electrodes have good connection.