Signal Encoder of Real-Time Bio-Aerosol Counter Using 280 nm UV-LED Induced Fluorescence

Real-time monitoring of bio-aerosols in the atmosphere has gained importance in both military and civilian security. As the first stage of defense architecture, a fluorescent particle counter is a compact, low-power, fast response sensor capable of giving a tentative warning. In this research, we developed a novel signal encoder for low power real-time fluorescent particle counter. Using a single 280 nm UV-LED light source and an acceleration nozzle, the particle counts are binned to three sizes: 0.84-2, 2-5, and 5- 11~\mu \text{m} . Integrated fluorescence is measured in 308-420 nm. Optimization of pulse width thresholds on the fluorescence channel based on fluorescent particle detection accuracy is demonstrated. Proposed size distinguishing scheme achieves accuracy of 0.853 compared to 0.823 for accuracy of single bin counterpart. The adaptive window scheme improves the dynamic range of particle counts. Further, the count efficiency improved by 0.394 for input count rate of 10 4 sec −1 compared to fixed size window scheme. Counting performance comparison with an APS validates good linearity of R 2 = 0.984. As the device showcases high dynamic range, linearity, and detection accuracy, we expect that it can serve as a useful tool in ambient environment monitoring, especially concerning airborne fluorescent particles.