If Fp1 and F3 forms a differential V+, V- and
F3 and C3 forms another differential V+, V- and
C3 and P3 forms another differential V+, and V- and
P3 and O1 forms another differential V+, and V-

What noises could be introduced to say the F3 and C3 channel with them connecting to another pair (as illustrated above)?

 

The paper Removing Noise From Electroencephalogram Signals For BIS Based Depth of Anaesthesia Monitors says "The noises in EEG signal are from the muscle, eye movement and blinking, power line, and interference with other devices.
core.ac.uk

The article How to Reduce Noise in EEG Records [11 Solutions] might be of interest.
https://mentalab.com/reduce-noise-in-eeg-recordings/

 

In the image text, shouldn't "F3-F3" be "F3-C3"?

ak

 

Do they use differential V+, V- between the points in the montage with Common Mode rejections or do they just deduct the positive signal in each points? In this latter case, is there any Common Mode rejections?

 

The output is the differential voltage with high CM rejection. The AD8422 exhibits >80 dB CM rejection at 10 kHz. And, LTSpice has the AD8422 model.

Analog Devices EGG measurement solutions
https://www.analog.com/en/solutions/healthcare/vital-signs-measurements/eeg-measurement.html

AD8422 https://www.analog.com/en/solutions/healthcare/vital-signs-measurements/eeg-measurement.html

 

Are all 16 channel EEG amplifier like that? But in the case of the g.USBamp (see below). The gUSBamp has 16 inputs with positive amplification, and 4 reference inputs with negative amplification. It always measures the differences between positive inputs, and associated reference. If you switch to "bipolar", it will simply take the difference between two inputs with positive amplification not in hardware but in DSP software. Does it mean there is no Common Mode rejection?

 

I have confirmation the g.USBamp bipolar is not real differential meaning no common mode rejection. But I'm not sure if the channel 1 to 16 is differential with respect to the blue reference (V-) at bottom or it just deducts the signal without any common mode rejection. Is there a way to test if the inputs are differential or not?

 

Guys. Is it true that in DSP based bipolar mode like in the g.USBamp above where say channel 2 was deducted from channel 3 by DSP firmware only. The common mode can be deducted as well. So it's like the instrumentation amplifier differential and common mode can be duplicated in pure ADC? For example. If you subtract the signal of channel A from the signal of channel B, you will automatically cancel any signal C that is common to both:
A = A_0 + C, B = B_0 + C, B - A = B_0 + C - A_0 - C = B_0 - A_0.

This can be done by any software that is able to perform a subtraction of channel data,