# Automated Low Investment Cost Evaporometers (ALICEs)
## 4 Discussion  
Testing of the experimental capacitance measurement did not give a clear result. Values observed in the dry and submerged conditions clearly differ, nonetheless removing the noise observed on the values between these two extremes was beyond our capacity. The construction of a complex professional capacitance water level measurement sensor needs greater depth of electronics knowledge to construct a signal conditioning circuit. The contact capacitive approach does not need any conditioning circuit. All special electronics are factory made on the bought Arduino sub-board. Thus, this design is more suitable for environmental engineers, who do not have a full electronics background. The contact capacitive approach also promised a much better result because the values are not continuous but discrete, thus reading of the data should be easier. Additionally, there is no need for continuous sub-millimeter reading precision. In preliminary testing, we used a prototyping board (Perfboard) with different lengths of wires soldered on. After a long run of several days in submerged conditions, submerged copper surfaces started to develop greenish crystals and white crystals started to develop on soldered covered surfaces. However, the principle of measurement worked, as when the water level dropped below the soldered-on wire end, the capacitor was disconnected, and the total capacitance also dropped. The first prototype was equipped with 3D printed electrodes made of conductive PLA. This material has shown good results for ease of printing and for stability in a water environment. However, the device equipped with 3D printed contact electrodes did not work. To further investigate why the conductive filament did not work, we tested resistivity of the materials. Conductive filament gave a value of 2.3 k\(\Omega\). Stainless steel gave a value of 0.5 \(\Omega\). This large difference between resistivities of the materials convinces us that resistivity is one of the main problems when using conductive filament as a needle material. Another problem can be the screwed connections of the printed needle and copper plating of PCB. Thus, we switched from 3D printed electrodes to stainless steel electrodes, and the device started to work. For this reason, we decided to use stainless steel for electrodes. Stainless steel requires a special soldering liquid for soldering, but this liquid is readily available. Stainless electrodes proved to be a viable solution to problems with electrolytical erosion and after the experiment, no corrosion was found on the electrodes. Evaluation of the electrodes was carried out under a magnifying glass with an LED light. No discoloration was found on the surface of the stainless steel electrodes, and sharp points were still sharp and sturdy. Data were successfully saved on the SD card and no loss of data was observed. The real-time clock worked perfectly, and there was no time distortion. The first prints were made with PLA plastic. This material showed good results for precision, for ease of printing, and for assembly. However, during reliability testing, the print of this material was severely deformed due to sun exposure. Testing continued with the universally used PETG plastic. This material proved to be reliable and stable enough, so it was chosen to be the final material. The PETG plastic material withstood the water immersion without any problems. The surface of the printed device was coated with limescale after the water evaporated. Although the device was not protected against sunlight, no distortion of the plastic structure was found. The data shown in Figures 5 and 6 show a continuous decrease in the measured value and clear steps on the graph at the moment when the needle was disconnected from the circuit. This proved the working principle of the measurement method. In general, the contact capacitive measurement principle proved to be much more precise in a simple configuration than resistance-based measurement, which can be used as a preliminary approach to a problem.