*4.2. Selection of Calculation Method*

In the climbing stage, the smaller GC is, the larger the difference is in the three-point sampling and the smaller the result error is. If GC is too small, the sampling may reach the stable stage after climbing, the difference between the three sampled voltages will be too small, and the resulting error will increase. The accuracy is the highest only when the three sampled voltages are in the climbing stage of the voltage variation curve. Equation (6) shows that when the difference of the three sampled voltages is close to zero, the calculated value of ∆*E*<sup>1</sup> is nearly infinite because of signal interference in the actual application unlike in the ideal situation. This condition seriously affects the measurement result. A positive constant is set as *C<sup>a</sup>* to determine if GC is too small by using the following rule.

$$\begin{cases} v\_{11\\_2} - v\_{11\\_3} < \mathcal{C}\_\mathbf{a} \\ v\_{22\\_2} - v\_{22\\_3} < \mathcal{C}\_\mathbf{a} \\ v\_{12\\_2} - v\_{12\\_3} > -\mathcal{C}\_\mathbf{a} \\ v\_{21\\_2} - v\_{21\\_3} > -\mathcal{C}\_\mathbf{a} \end{cases} \tag{13}$$

If the three sampled voltages satisfy Equation (13), then GC is too small to be non-negligible, and the traditional sampling method is adopted. If the three sampled voltages do not satisfy Equation (13), then GC is non-negligible, and the proposed three-point climbing algorithm is adopted.
