# Mitigating Electrochemical Effects in Resistive Frost-Detection Sensors
## 3 Results  
The experiment was conducted over a 5 h and 45 min period. Both sensors were subjected to a 5 V excitation: the continuous sensor remained constantly powered, while the pulsed sensor received 5 V for 50 ms every 3 s. To streamline analysis and improve result visualization, the recorded data were post-processed to a 60 s interval, filtering out redundant measurements. As shown in Figure 8, the results reveal a clear distinction between the two sensor measurement methods. The measurements obtained using the continuously powered sensor method were highly erratic; the resistance values fluctuated unpredictably between a maximum of 16.0 k\(\Omega\) and a minimum of 1.4 k\(\Omega\). The curve exhibited irregular, sharp drops and jumps, showing considerable instability throughout the measurement process. In contrast, the pulsed DC excitation sensor reading method produced a much more stable curve, displaying a concave downward shape with a decreasing slope. The resistance started at 16.1 k\(\Omega\) and gradually decreased to 14.4 k\(\Omega\), where it stabilized. This behavior occurs because, although the duty cycle is very low, the brief application of voltage is sufficient to increase ion presence, reducing water resistivity. However, due to the reversible nature of the reaction (as shown in Equation (5)), the resistivity decline eventually levels off as equilibrium is reached between ion formation during the 50 ms pulses and ion recombination (neutralization). As seen in Figure 9, during testing with the pulsed DC excitation method, no visible changes occurred in the electrodes or the water; this outcome is consistent with the experiment's objectives. It should also be noted that in the top row of Figure 9, from \(t=0:00\) h to \(t=1:30\) h, the time interval between pictures is \(0:30\) h, whereas in the bottom row, from \(t=2:30\) h to \(t=5:30\) h, the interval is \(1:00\) h. The timestamps are also marked in the graph of Figure 8 with vertical dashed bars to facilitate the analysis. The results from the continuously powered sensor reading method reveal markedly different outcomes, as shown in Figure 10.  
Figure 8: Comparison of measurement results between continuous voltage sensor readings and pulsed DC excitation sensor readings. Figure 9: Sensor electrodes during testing for the pulsed DC excitation method. Multiple electrochemical reactions occur both at the electrodes and within the water, developing over time as shown in Table 1.  
At this time, gas bubbles are clearly observed forming near both electrodes, a blue substance is noticeably present on the left side of the anode, and the cathode has developed a polished, reflective surface. All three phenomena were already present at \(t=0\):05 h; however, at that earlier time, the polished surface was fully formed, while the blue substance and gas bubbles were nearly imperceptible, only becoming more noticeable around \(t=0\):20 h.  
The blue layer on the anode grows significantly, and gas bubble production continues, but significantly more at the cathode, where hydrogen gas bubbles dislodge and flow to the surface at smaller sizes, contrary to the oxygen bubble that grows on the electrode surface. The lower part of the blue precipitate spreads to about half the distance between electrodes and begins to become dark. The blue layer on the anode continues to expand toward the cathode and begins dislodging from the electrode, precipitating into the solution. Simultaneously, the cathode develops a progressively darker appearance as a black material starts to coat the entire electrode surface. The upper portion of the blue material dislodges from the anode and connects to the top region of the cathode. The bottom section also detaches and bends toward the cathode, where it begins to become dark, particularly near the cathode. Meanwhile, the black substance continues to accumulate around the cathode surface, with a more significant buildup on the side facing the anode.