EEG readings amplitudes


#1

Hi,

I cannot figure out why /muse/eeg output is on average 800 µV, while the usual amplitude values are 10 µV to 100 µV. Shall I apply a correction to recover typical values?

Thanks


#2

Hi there,

The 800uV DC offset is to be expected. See my answer from this thread:

There will always be a DC offset in the EEG data. The offset is in REF as well as the data, because due to the amplifier configuration in Muse the DC difference is not amplified, just the AC difference is. The offset appears un-amplified at the input to our ADC, and is approximately at the ADC’s midpoint. If you use the conversion factor that we mention in our documentation to convert amplified ADC values to uV, this comes out to around 800uV. However, the conversion factor is calculated to account for AC signals that have been amplified, and remember, the DC offset does not get amplified.

So the 800uV mean is not [I]really[/I] 800uV. But it’s not [I]really[/I] the mean that you’re interested in. The long-term mean of the signal is probably useful for only a few things like the skin-electrode half cell potential. Really what you’re interested in is the peak-to-peak amplitude of signals, whether they be slow or fast-changing. Even if you want to investigate the behaviour of a signal which changes very slowly, the useful information is contained in how it changes, not in what mean it is centred around.


#3

got it, thank you Tom.