# Mitigating Electrochemical Effects in Resistive Frost-Detection Sensors
## 4 Discussion  
To clarify the differences in measurement behavior between excitation methods, key statistical indicators--mean, standard deviation, coefficient of variation, and variance--were calculated for both datasets. The pulsed method yielded a mean resistance of 14.77 k\(\Omega\), with a standard deviation of 0.47 k\(\Omega\) and a coefficient of variation of 3.17%, indicating a stable and consistent measurement profile. In contrast, the continuous excitation method produced a lower mean of 5.11 k\(\Omega\), but with a much higher standard deviation of 4.34 k\(\Omega\) and a coefficient of variation of 84.97%, reflecting significant fluctuation and instability in the signal. The variance values reinforce this distinction: 0.22 k\(\Omega^{2}\) for the pulsed method versus 18.83 k\(\Omega^{2}\) for the continuous method. These metrics demonstrate that pulsed excitation leads to more consistent readings with reduced noise, while continuous excitation results in higher dispersion, potentially due to progressive electrode degradation or polarization effects. A summary of the descriptive statistics for both methods is presented in Table 2.  
A paired-samples \(t\)-test was also performed to analyze the significance of the differences observed between the two excitation methods. The test compared paired resistance values collected simultaneously from both the pulsed and continuous excitation methods. The resulting \(t\)-statistic was 196.50, with a \(p\)-value below 0.001, indicating a significant difference between the two datasets. This result confirms that the differences in mean resistance values are not due to random variation but are statistically meaningful. The \(t\)-test thus reinforces the findings already evident from the variance, standard deviation, and coefficient of variation, confirming the improved stability of the pulsed excitation method. Unstable measurements were also visibly identified by high amplitude fluctuations and abrupt resistance variations observed in Figure 8, supporting the statistical results. Visual inspection through high-resolution photography further indicated electrode degradation associated mostly with continuous DC excitation, evidenced by apparent electrochemical degradation. In addition to qualitative observations, Figures 11 and 12 provide a quantitative perspective on electrode surface changes by tracking the accumulation of black and blue materials over time. The percentage of black pixels, associated with material buildup on the cathode, increased sharply in the sensor powered by the continuous DC excitation method, peaking at 25% by \(t\) = 4:00 h, whereas the sensor subjected to the pulsed DC excitation method maintained a low and stable level below 1.2% throughout the test. Similarly, the anode showed a progressive increase in the percentage of non-black and non-red pixels--corresponding to blue material--in the continuous DC excitation condition, reaching over 27% at the peak. The pulsed DC method again demonstrated more stable results, with percentages remaining below 3%. The slight decrease in values observed toward the end for the electrodes powered using the continuous excitation method is attributed to the precipitation of the formed substances outside the cropped region analysed for this method. The result analysis is based on the understanding that the materials involved are copper and distilled water subjected to an electric field. Based on the observed colors of the materials deposited on the sensor electrodes--black and blue--two compounds are identified as the likely candidates. The black material \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **Mean (k\(\Omega\))** & **Standard Deviation (k\(\Omega\))** & **Coefficient of Variation (\%)** & **Variance (k\(\Omega^{2}\))** \\ \hline Pulsed DC & 14.77 & 0.47 & 3.17 & 0.22 \\ Continuous DC & 5.11 & 4.34 & 84.97 & 18.83 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Descriptive statistics for resistance measurements under different excitation methods.