Low-cost particulate matter (PM) sensors based on the light scattering principle measure the concentration of particles by the change of scattering intensity after light is irradiated onto the particles. It has been reported that when the relative humidity is high, water vapor may cause the expansion of airborne particles and affect the accuracy of the light scattering method for PM measurement, but it has also been shown that the effect of humidity is not significant or even negligible. Therefore, to determine the effect of humidity on the Plantower PMS7003 light scattering sensor, in this study, a BAM1020 (Beta Attenuation Monitoring) was installed alongside to continuously monitor the ambient atmospheric PM concentration for approximately four weeks. The sensors collected data at 10-minute intervals, resulting in a 1-hour average for comparative analysis. To accurately measure humidity, the performance of the Arduino + DHT22 humidity sensor was also pre-evaluated using a series of saturated salt solutions. The humidity was grouped into five intervals and analyzed by visual analysis. The results confirmed that there was no significant correlation between PM2.5 differences and humidity, which were randomly and uniformly distributed around the mean. However, since in the very low and high concentration ranges based on the beta-ray monitor measurements, the difference between the light scattering sensor PM10 measurement and the reference value is much larger than the difference between the PM2.5 and the reference value., there is an additional need to investigate the appropriate correction method for dust season or PM10. The results show that the outcomes of the light scattering sensor are more influenced by particle size and concentration than by humidity.

본 연구는 토마토 수경재배에서 Frequency Domain Reflectometry(FDR) 센서를 활용한 무배액 시스 템에 적합한 코이어 배지의 chip과 dust 비율을 구명하기 위한 기초 실험으로 chip 함량에 따른 일일 급액량, 배액량, 배지의 용적당 수분함량 및 전기전도도, 식물생육, 과실 수량과 수분이용효율 측정을 목적으로 수행되었다. 시판 코이어 슬라브 중 chip과 dust 부피비율이 0 : 100%, 30 : 70%, 50 : 50%, 70 : 30%인 것과 대조구로 시판 rockwool 배지와 2층 슬라브, 즉 1층에 chip함량과 2층에 dust함량이 15 : 85%, 25 : 75%, 35 : 65%인 것을 사용하여 실험하였다. 실험에 사용된 배지 중 0 : 100%와 rockwool 배지는 전 생육기간 동안 배액이 배출 되지 않았고 나머지 모든 배지에서도 극소량의 배액이 배출되었다. 일일 평균 급액량은 시판 슬라브와 2층 슬라브 배지 모두에서 chip 함량에 따라 다르게 나타났다. 식물 생육, 상품과 수량 및 수분이용효율은 chip과 dust의 비율이 0 : 100%인 시판 슬라브에서 가장 높게 나타났다. 따라서, FDR센서에 의한 자동급액 방식으로 토마토 작물을 재배 할 때 chip과 dust 부피비율이 0 : 100%인 코이어 배지를 사용할 경우 식물이 더욱 효과적으로 수분을 이용하여 생산량이 증가되면서도 배액을 최소화하거나 배액을 창출하지 않아 환경오염을 감소시킬 수 있다. FDR 센서에 의해 자동 급액되는 시스템에서 1회 급액량과 급액간격 기능을 생육단계별로 조정하여 배지의 물리성에 따른 급액 일정에 대한 세밀한 실험이 앞으로 수행될 계획이다.

A three-staged cascade virtual impactor was designed, fabricated, and used as aerosol classifier in a dust sensor module. The dust sensor module consisted of the impactor, three commercial dust sensors, and four pumps. For the design of the impactor, three cut-off diameters of 2.5 ㎛, 2.0 ㎛, and 1.5 ㎛ were selected. Then three nozzle widths were determined from computational fluid dynamics (CFD) simulation with the three designed cut-off diameters. </br>Laboratory generated PM2.5 aerosols classified into each of three sizes, via the fabricated impactor, entered a dust sensor from which voltage signals were detected due to particle scattering by a laser diode in the sensor. The voltage signal data from the three sensors were converted to number concentrations of the dust particles utilizing correlation equations obtained from separately performed experiments. The number concentrations were in agreement with those obtained by aerodynamic particle sizer (APS).