# Remote Water Quality Monitoring System for Use in Fairway Applications
## 2 Materials and Methods
### Remote Water Quality Monitoring System Architecture
The measurement ranges include pH from 2.00 to 12.00, temperature from \(-5\)\({}^{\circ}\)C to 60 \({}^{\circ}\)C, salinity from 0 to 10.00 ppt, oxygenation from 0.0 to 199.9% (0.0 to 30.0 mg/L), and conductivity from 0 to 1999 \(\upmu\)S/cm;
* **Elmetron--CX-705 Multifunction Instrument:** This is a highly accurate laboratory instrument that can also be used in the field. In addition to measuring pH, redox potential, conductivity, salinity, resistance, ions, dissolved oxygen (both in water and air), atmospheric pressure, and temperature, it has a semi-automatic titration function. The device offers measurement ranges for various water parameters and includes temperature and atmospheric pressure compensation features;
* **SensoDirect 150 Multi-parameter Meter:** This portable multi-parameter meter from LOVIBOND TINTOMETER enables rapid and accurate measurements of pH/redox, dissolved oxygen, and conductivity/TDS. It provides measurement ranges for pH, ORP, dissolved oxygen, conductivity/TDS, and temperature. The research was conducted in a laboratory environment, where a Water Environment Simulation Setup was constructed. The central component of the setup is a 240 L aquarium, providing sufficient space for simulating an aquatic environment. The aquarium's dimensions are standardized, ensuring precise execution of experiments and observations of aquatic organisms' behavior. Additionally, the aquarium lighting system was designed to simulate the natural day-night cycle, allowing the study of light variations' effects on aquatic life and accelerating potential fouling of the sensors being tested. Furthermore, an external flow-through heater with adjustable power was implemented to maintain a stable water temperature in the aquarium. Maintaining the correct water temperature is critical for the health of aquatic organisms and for simulating realistic environmental conditions. The study was conducted in a simulation setup using water collected from the river, with a day-night cycle simulated and microorganisms introduced to test the potential for sensor overgrowth. The selected sensors were tested under conditions resembling real-world scenarios to confirm their effectiveness and accuracy. Physical clogging of the buoy was not considered due to ongoing work on optimizing the buoy design to prevent floating debris from blocking the sensors. Discussions with sampling teams and our research showed that within the interval between cleaning and calibration (1 month), no sensor overgrowth was observed. Field studies are planned for the next stages after improving the buoy design. The testing and calibration process involved laboratory calibration by verifying measurement accuracy in controlled conditions. Both laboratory and field tests demonstrated that the use of three different sensors measuring four parameters would be the optimal technological and economic solution for the buoy-based water quality assessment:  
* Gravity--Analog pH Meter V2 (SEN0161-V2) [39]: This analog pH sensor offers accurate measurements of the acidity and alkalinity of aqueous solutions. Powered by 3.3 V to 5.5 V, it generates an output signal ranging from 0 V to 3 V. It includes a laboratory-grade probe and operates within a pH range of 0 to 14 with an accuracy of \(\pm\) 0.1 pH at 25 \({}^{\circ}\)C. An integrated LED, BNC connector, and PH2.0 interface make it easy to integrate with Arduino systems (Leonardo). * DFRobot Gravity--Analog Dissolved Oxygen Sensor X (SEN0237-A) [40]: This analog sensor, compatible with Arduino, provides high-precision measurements of dissolved oxygen levels in water. Powered by 3.3 V to 5 V, the output signal ranges from 0 V to 3 V. It features a galvanic probe that connects easily via a BNC connector. The detection range of 0 to 20 mg/L allows for effective water quality monitoring. The sensor also has durable electrodes and can be maintained based on the type of water used.