Experiencing apparent line noise when using Quattrocento

#1 · 1 Marzo 2024, 20:07

We are using the Quattrocento, AD64F, and GR04MM1305 to collect 64 channels of EMG data (placed on forearm). When plotting the waveforms in Biolab+, we see that the ground appear to be affected by a noise source since they appear to show the same waveform (we assume line noise since it roughly appears to be oscillating at 60Hz, see attached image). Namely, at baseline (eg when no muscle are active), all of our channels are correlated, whereas we would expect to see very small random variations independent across the channels.

We are assuming this is a grounding issue, but so far have not been able to ameliorate it. We originally tried with the arm bands included with the Quattrocento package (tested them wet like directed), at the elbows and then wrists, then tried again but with them dry, and have since ordered sticky foam electrodes again placed on the elbows and later on the wrists. All of these have resulted in the same correlated baseline waveforms. We are in the city, not near power lines, as far as we know (perhaps it is bluetooth related or from other nearby hardware?).

Is this a known issues, or do you have any suggestions of what to try to ameliorate this noise? We are planning to move the hardware+desktop to its own room, away from other computers/phones/headphones in the lab environment.

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#2 · 5 Marzo 2024, 11:14

Hi and thank you to have opened this ticket, i give you some informations about the references of the Quattrocento. There are two references that you have to configure, the first is the patient ref reference, and we normally use a wet band strap placed in "bone" zone, like the wrist or the ankle, it is connected directly to the quattrocento. The second one is the adapter reference, also in this situation we normally use a wet bandstrap placed always in a bone zone but quite near to the matrix, the important think is that the two bandstraps have no to touch each other. Regarding the potential noise signals, there are different thinks that you can try to improve the quality of your signals, i share with you a link with a tutorial that show you how to do it (https://www.youtube.com/watch?v=omOwcGHHq8Y&ab_channel=OTBioelettronica). Let me know if this improve the thinks, if not write back in this ticket and i will try to help you.