noise from other devices

#1 · 26 Luglio 2024, 5:10

Hi,

I'm recording HDsEMG signals while performing isometric ankle dorsiflexion and knee extension on the HUMAC Cybex system. The grid is on the TA (or VL for knee extension), the ground is on the wrist and the reference is on the knee. The signals look perfectly fine when not touching the Cybex, but as soon as you touch the Cybex, the noise in the HDsEMG signals increases significantly. Is there a way to prevent the noise from the Cybex negatively affecting the EMG signals? (e.g. using a different reference/ground setup)

Thank you very much

Have a nice day

Patricia

#2 · 26 Luglio 2024, 9:57

Hi Patricia,

Your setup and ground positioning looks good to me. The problem could be related to the earth of the Humac system. If everything is fine (and follows electrical safety rules), the system if connected to the earth of the room. You could get some noise but it should be acceptable.
You should verify is the system is connected to the earth. Is the HUMAC Cybex connected to the power line? Is it connected to the ground of the room electrical plant?
If not sure, you could try to find a screw or another metal component (no paint on it, it must be in metal) and try to make it in contact with the earth of the room, for example using a double head crocodile cable.
As alternative if safety is verified you can also connect Humac system to OTB device (Quattrocento?) patient ref.

I attach also a screenshot taken from this website:
https://www.victronenergy.com/media/pg/The_Wiring_Unlimited_book/en/ground,-earth-and-electrical-safety.html#:~:text=To%20make%20electrical%20installations%20safer,the%20path%20of%20least%20resistance

Simone

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