Table 1. Mathematical descriptions of the extracted 7 features.

Extracted features
Minimum voltage	Vmin = min(Xn)
Maximum voltage	Vmax = max(Xn)
Mean voltage	$V_{\text{mean}}=\frac{1}{N}·{\sum }_{n=1}^N{X}_n$
Voltage range	Vmean = Vmax − Vmin
Average signal power	$P_{\text{signal}}=\frac{1}{N}·{\sum }_{n=1}^N{X}_n^2$
Rate 0 voltage crossings	$R_{0-\text{cross}}=\frac{1}{N-1}·{\sum }_{n=1}^N[sign(X_n-1)\ne sign\left(X_n\right)]$
Rate of samples above 0 volts	$R_{\text{positive}}=\frac{1}{N}·{\sum }_{n=1}^N(X_n\ge 0)$