AN OPTICAL MONITORING SYSTEM BASED ON DOUBLE-BARRIER SILICON PHOTORECEIVERS
Keywords:
optical monitoring, double-barrier photodetector, spectral analysis, LoRaWANAbstract
Optical monitoring systems are widely used for the analysis of transparent media in agriculture, ecology, food, and medical industries. Modern requirements for such systems include high precision, mobility, and cost-effectiveness, which makes the development of compact solutions for laboratory and field research particularly relevant.
This work presents an optical monitoring system based on double-barrier silicon photoreceivers, which offer high spectral sensitivity in the range of 350…900 nm. Previously, prototypes of photoreceivers were developed, including algorithms for processing spectral data. However, to create a complete monitoring system, it was necessary to solve the problem of integrating the photoreceivers into a compact device with a wireless interface and remote control capabilities.
The LoRaWAN protocol was chosen as the optimal communication technology, providing a communication range of up to 10…15 km and ultra-low power consumption. The hardware platform includes an adjustable light source, precision analog-to-digital and digital-to-analog converters, a microcontroller for data processing, and an LCD for visualization. An automated procedure for measuring the current-voltage characteristics (I–V curves) of the photodetector was implemented, with subsequent processing in the LabVIEW environment. The system allows for the determination of wavelengths, their intensities, and includes a comparison function with permissible concentration limits of substances, providing alerts in case of deviations.
Testing of the system prototype confirmed the measurement accuracy (±2%) and low power consumption (15 mW). The system demonstrates an accuracy comparable to commercial counterparts when determining concentrations (error of 3.5% for nitrates), but at a lower cost.
Future development prospects include expanding the spectral range and optimizing the algorithms. The system can be applied for autonomous monitoring of liquid media in industry, environmental monitoring, and medicine.
