Journal of Bio-Environment Control (생물환경조절학회지)

The Korean Society for Bio-Environment Control (한국생물환경조절학회)
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Real-time Nutrient Monitoring of Hydroponic Solutions Using an Ion-selective Electrode-based Embedded System

ISE 기반의 임베디드 시스템을 이용한 실시간 수경재배 양액 모니터링

  • Han, Hee-Jo (Department of Biosystems Engineering and Biomaterials Science, College of Agriculture and Life Sciences, Seoul National University) ;
  • Kim, Hak-Jin (Department of Biosystems Engineering and Biomaterials Science, College of Agriculture and Life Sciences, Seoul National University) ;
  • Jung, Dae-Hyun (Department of Biosystems Engineering and Biomaterials Science, College of Agriculture and Life Sciences, Seoul National University) ;
  • Cho, Woo-Jae (Department of Biosystems Engineering and Biomaterials Science, College of Agriculture and Life Sciences, Seoul National University) ;
  • Cho, Yeong-Yeol (Major of Horticultural Science, Jeju National University) ;
  • Lee, Gong-In (Department of Agricultural Engineering, National Institute of Agricultural Sciences)
  • 한희조 (서울대학교 농업생명과학대학 바이오시스템소재.공학부 바이오시스템공학전공) ;
  • 김학진 (서울대학교 농업생명과학대학 바이오시스템소재.공학부 바이오시스템공학전공) ;
  • 정대현 (서울대학교 농업생명과학대학 바이오시스템소재.공학부 바이오시스템공학전공) ;
  • 조우재 (서울대학교 농업생명과학대학 바이오시스템소재.공학부 바이오시스템공학전공) ;
  • 조영열 (제주대학교 원예환경전공) ;
  • 이공인 (농촌진흥청 국립농업과학원 농업공학부)
  • Received : 2020.01.21
  • Accepted : 2020.04.10
  • Published : 2020.04.30
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Abstract

The rapid on-site measurement of hydroponic nutrients allows for the more efficient use of crop fertilizers. This paper reports on the development of an embedded on-site system consisting of multiple ion-selective electrodes (ISEs) for the real-time measurement of the concentrations of macronutrients in hydroponic solutions. The system included a combination of PVC ISEs for the detection of NO3, K, and Ca ions, a cobalt-electrode for the detection of H2PO4, a double-junction reference electrode, a solution container, and a sampling system consisting of pumps and valves. An Arduino Due board was used to collect data and to control the volume of the sample. Prior to the measurement of each sample, a two-point normalization method was employed to adjust the sensitivity followed by an offset to minimize potential drift that might occur during continuous measurement. The predictive capabilities of the NO3 and K ISEs based on PVC membranes were satisfactory, producing results that were in close agreement with the results of standard analyzers (R2 = 0.99). Though the Ca ISE fabricated with Ca ionophore II underestimated the Ca concentration by an average of 55%, the strong linear relationship (R2 > 0.84) makes it possible for the embedded system to be used in hydroponic NO3, K, and Ca sensing. The cobalt-rod-based phosphate electrodes exhibited a relatively high error of 24.7±9.26% in the phosphate concentration range of 45 to 155 mg/L compared to standard methods due to inconsistent signal readings between replicates, illustrating the need for further research on the signal conditioning of cobalt electrodes to improve their predictive ability in hydroponic P sensing.

본 연구는 양액 내 존재하는 다량 영양소의 농도를 실시간으로 측정하기 위해 이온 선택 전극 (ISE) 으로 구성된 임베디드 시스템의 개발을 보여준다. NO3, K 및 Ca 이온을 감지하기위한 PVC ISE, H2PO4를 감지하기위한 코발트 전극, 기준 전극, 샘플 용액이 담기는 챔버, 펌프 및 밸브를 사용하여 측정하는 시스템으로 구성된다. 양액 샘플양 조절과 데이터 수집을 위해서 데이터 Due 보드가 사용되었고, 각각의 샘플 측정 전에, 측정 중 발생하는 드리프트를 최소화시키기 위해 2 점 정규화 방법을 사용하였다. PVC 멤브레인을 기반으로 한 NO3 및 K 전극의 농도 예측 성능은 표준 분석기의 결과와 근접한 일치 (R2 = 0.99) 나타내며 만족스러운 결과를 나타냈다. 하지만, Ca II 이온 투과체 제조된 Ca 전극은 고농도 양액 농도에서 Ca 농도를 55 %로 낮게 측정하였다. 코발트 전극 기반 인산 측정은 반복측정 중에 발생한 코발트 전극의 불안정한 신호로 인해 표준 방법과 비교하여 45 ~ 155 mg / L의 인산 농도 범위에서 24.7 ± 9.26 %의 비교적 높은 오차를 나타냈다. 수경 P 감지의 예측 능력을 향상시키기 위해 코발트 전극의 신호 컨디셔닝에 대한 추가 연구가 필요함으로 판단된다.

Keywords

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