fig2

Figure 2. Wearable bioelectrical signal acquisition unit and sEMG electrode arrays. (A) Schematic diagram and photograph of the sEMG acquisition unit, showing both the internal circuitry and the external appearance; (B) Electrode layout of the D64 array; (C) Electrode layout of the R64 array; (D) Example sEMG signals recorded from selected electrodes (blue points) in (B); (E) Example sEMG signals recorded from selected electrodes (red points) in (C); (F) Illustration of the SNR of the R64 and D64 arrays. Gestures are divided into four groups for visualisation, and the D64 array also includes colour-coded regions corresponding to different muscle groups. sEMG: Surface electromyography; D64: 64-channel distributed electrode array; R64: 64-channel ring electrode array; SNR: signal-to-noise ratio; PMU: power management unit; LED: light-emitting diode; AD: analog-to-digital; RF: radio-frequency.