How is electrode contact measured?

[Kenzo85]

When I connect my Muse, the colored circles show if my electrodes are connected or not. But sometimes this isn't working. How exactly is this calculated to be in the acceptable range or not?

[James]

The code for this is supplied by Interaxon in their closed source SDK, so I can't tell you specifics, but it's based on the variance of the RAW EEG channel for each electrode. The lower the min/max the better the connection. EMG interference and poor sensor contact causes higher min/max variance, where as EEG will only show a very low variance due to brainwaves being such low electrical power.

[ClintBarrett]

First, make sure that the electrodes are properly connected to your head and that they fit snugly against your skin. If the electrodes do not fit against your skin, they will not be able to measure the electrical potential of your brain. Second, make sure that you are using the correct types of electrodes and that they are in good condition. If the electrodes are damaged or defective, they will not measure electrical potential correctly.

[Kenzo85]

Thanks for the reply James! If I wanted to implement a sensory quality indicator (like horseshoe) in my app, how could I access this by using Muse's SDK?

[James]

Assuming you mean using Mind Monitor's OSC data stream, "/muse/elements/horseshoe" has the horseshoe data in it.
Also, you'd need "/muse/elements/touching_forehead" for the top black oval.
https://mind-monitor.com/FAQ.php#oscspec

[Kenzo85]

I meant how is your app accessing this data? (I know this is a selfish question lol).

[James]

If you want to use the Muse SDK, you can pay Interaxon for a monthly license plus sales royalties and they will give you the documentation

[Kenzo85]

Haha thanks for the info!

[Kenzo85]

Sorry to bombard, but right now the Muse sends packets via bluetooth to the phone. Why can't FPz data (contact etc) be picked up in bluetooth? As in the 'touching_forehead' parameter. Or is it because this info isn't sent in bluetooth packets directly, rather it can be only be inferred based on the signal/packets from the other 4 electrode channels?

[James]

Yeah, it's just bluetooth data packets, if you want to try and read it direct, you can. It's complex though and I can't help you with their proprietary data format.