When you should use the notch?

eeg
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#1

Hi Im a technologist from Asia. My machine is set to 50hz notch… I use it sometimes to reduce the noise that cause interference on my recording. But some of the doctors/readers don’t want it to be turn on when performing the procedure or touching those filters high/low cut. This things are avoidable. I can’t get a perfect recording always especially when your doing it on bedside like wards/ICU or any part of the hospital. Any suggestions to improve it with touching those filters or can anyone give at least explanation about notch and other filters. Thank you in advance.

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#2

Jigs, hi.

Use of a mains noise notch filter is VERY common in EEG. Do the doctors understand that technical point? Mains noise is ubiquitous and unavoidable since the power conduits, cables and cords are always within some meters of us when we are in any room.

The magnetic fields from power cables and lines are especially strong around power adaptor boxes, that convert from mains to DC power for computers and equipment. Position your EEG gear as far from adapters, cables, conduits as you can.

Also be sure to have a good ground lead connection to the EEG amplifier. On some EEG equipment the ground lead is used to inject an out-of-phase mains signal at low level, to counteract what is known as common-mode noise. It helps in these cases if your ground lead is on a central axis so it reaches all parts of the head easily. For example on Electro-cap, they suggest 10-10 location AFz for the ground.

Regards,

William

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#3

thank you so much William.

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