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Everything you need to know about reference sensors of EMOTIV hardware

EPOC+ and EPOC X have two options for positioning CMS (common mode sensor) either at P3 location (slightly left of centre) or on the left mastoid location. DRL (common mode cancellation sensor) can be placed symmetrically on the right side. INSIGHT places both CMS and DRL on the left mastoid location. EPOC Flex (all models) allow completely arbitrary placement of both CMS and DRL reference sensors. EPOC Flex uses the same referencing circuit and strategy as EPOC X. EPOC Flex allows you to position the references anywhere you want them. Ear clips are available for Emotiv EPOC Flex Gel.

Where are the reference sensors? Do you have an impedance check for the hardware? Our electronics use CMS/P3 (left side) as the electrical reference point and DRL/P4 (right side) as the noise cancellation electrode. We use a CMS/DRL common mode cancellation circuit which includes injection of a small high-frequency signal into DRL. We measure the amplitude of that signal at each sensor location to determine the conductivity in real-time, fed back to the user through the contact quality map, with black/red/orange/green indicators at each location. M2/CMS2 and M1/DRL2 are alternative reference sensors. The cover rubbing should go to M2/CSM2 and M1/DRL2.

We use CQ (Contact Quality) to evaluate the impedance and have CQ display in our software. It’s a visual representation of the current contact quality of the individual headset sensors. You can observe each sensor’s status in real-time to adjust sensors to optimize contact quality. The color-coding is Green (good), Orange (moderate), Red (poor), Black (very poor). You can refer to this for more information.

We have also updated our application to have the EEG quality (EQ) that can help to determine the quality of the signal based on multiple metrics. Each of these metrics is important in assessing whether the recording data accurately captures the underlying brain signal. More information about EQ can be found here.

Updated on 25 Apr 2024

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