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자기장을 이용한 지중 무선 SAW 집적 센서 측정 시스템 개발
김시혁(Sihyeok Kim),이기근(Keekeun Lee) 대한전기학회 2020 전기학회논문지 Vol.69 No.6
A wireless underground sensor system was developed based on magnetic antennas and SAW sensor. The developed sensor system can wirelessly detect the ambient temperature, humidity, and hydrogen gas leakage in buried utilities up to about ~1m in underground. By using SAW sensors with different resonance frequencies, it is also possible to analyze information from different locations in underground using one antenna which is located on the ground. A 260~300 MHz magnetic antenna generated a surface acoustic wave along the piezoelectric substrate, and the returned SAW energy from the reflection bars were reconverted to magnetic flux via the sensor’s interdigital transducer (IDT) and subsequently transmitted to a reader in upperground. The developed system showed stable performance regardless of underground media (water, air, soil). Sensitivity and linearity for the temperature sensor was 5.06 °/°C and 0.98 respectively. Sensitivity and linearity for the gas sensor was 1.1 °/ppm and 0.96 respectively. It was analyzed that the humidity sensor has 6 °/RH% sensitivity and 0.95 linearity.
자기 에너지를 이용한 지중 SAW 온도센서 구동 및 무선 측정 시스템 개발
김시혁(SiHyeok Kim),이기근(Keekeun Lee) 대한전기학회 2019 전기학회논문지 Vol.68 No.9
A wireless underground sensor system was developed based on magnetic antennas and surface acoustic wave (SAW) resonator to monitor temperature variations around buried utilities. A~250 ㎒ magnetic antenna generates a SAW along the piezoelectric substrate, and the returned SAW energy owing to the reflection bars on the sensor is reconverted to magnetic flux by the sensor’s interdigital transducer (IDT) and subsequently transmitted to a reader via magnetic antenna. By observing changes in the center frequency of the SAW sensor with temperature, we were able to monitor the underground temperature variations in real time. Temperature sensor was fabricated on a 128o YX LiNbO₃. In soil testing, a long readout distance was observed. The temperature sensors provided stable performance in terms of underground temperature changes, soil type, and soil compactness. The sensitivity and linearity for the sensor was 0.3 ㎒/℃ and 0.96, respectively.
표류 자기장을 통한 에너지 하베스팅 및 무선 센서 시스템 개발
정세윤(Seyoon Jung),김시혁(Sihyeok Kim),이기근(Keekeun Lee) 대한전기학회 2021 대한전기학회 학술대회 논문집 Vol.2021 No.10
전력 소모가 낮은 220V 가정용 전력선 주변에 형성되는 표류 자기장을 분리형 자계 하베스터를 제작하여 유도하였다. 전력전자회로 (Power Management IC, PMIC)을 설계해 고효율 정류 및 충전하였다. 선형 방식 전력 컨버터를 통해 하베스팅 에너지를 충전 및 방전을 자동으로 스위칭하고, 자외선 센서를 구동하였다. 자외선 센서는 UV SAW(Serface Acoustic Wave) 공진기를 기반으로 개발되어 주변의 UV 에너지 변화량을 모니터링한다. UV SAW 센서는 자외선에 민감하게 반응하고 탄성파 속도가 변한다. 반환된 SAW 에너지는 IDT (Interdigital Transducer)에 반환되고 송신용 안테나를 통해 수신용 안테나가 연결된 판독기로 무선 전송된다. 판독기를 통해 SAW 센서의 중심주파수 변화를 관찰함으로써 주변의 UV 에너지 변화를 실시간으로 모니터링하고 무선 통신한다.
배관 파이프 정렬 감지를 위한 자기장 기반의 포지션닝 센서 시스템 개발
정세윤(Seyoon Jung),김시혁(Sihyeok Kim),이기근(Keekeun Lee) 대한전기학회 2021 전기학회논문지 Vol.70 No.5
When a pipeline is inserted into the joint coupler, frequent fires and uneven fusion occur in a trial of fusion without reaching to a desired position. To solve the matters, a positioning sensor and sensor system were developed that provide the information of electrical signal to PC whether the cut surface of the pipeline has reached the correct position. The developed sensor system consists of two permanent magnetic tapes, two magnetic hall sensors, and a PC. As the magnetic tape and sensor were aligned in the center to center, a large magnetic strength was observed from the sensor. A large change in sensor signal was also observed as the aligned center was laterally misplaced. By comparing the values of the two sensors, a vertical alignment status of the pipeline was affirmed which provides whether the pipeline was located in the center inside the cylindrical joint coupler. Overall system performances were evaluated in terms of the length, width, thickness of the magnetic tape, and ambient temperature change. The output signal of the sensor was finally analyzed as an electric signal instead of magnetic strength that was transmitted to PC to determine whether the fusion process should begin.