• Asia-Pacific Journal of Atmospheric Sciences
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• 제54권4호
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• pp.639-648
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• 2018

The pyranometer for observing the solar radiation reaching the surface of the earth is manufactured by various companies around the world. The sensitivity of the pyranometer at the observatory is required to be properly controlled based on the reference value of the World Radiometric Center (WRC) and the observatory environment; otherwise, the observational data may be subject to a large error. Since the sensitivity of the pyranometer can be calibrated in an indoor or outdoor calibration, this study used a CSTMUSS-4000C Integrating Sphere by Labsphere Inc. (USA) to calibrate the sensitivity of CMP22 pyranometer by Kipp&Zonen Inc. (Netherlands). Consequently, the factory sensitivity of CMP22 was corrected from $8.68{\mu}V{\cdot}(Wm^{-2})^{-1}$ to $8.98{\mu}V{\cdot}(Wm^{-2})^{-1}$, and the result from the outdoor calibration according to the observatory environment was $8.90{\mu}V{\cdot}(Wm^{-2})^{-1}$. After the indoor calibration of the pyranometer sensitivity, the root mean square error (RMSE) of the observational data at the observatory on a clear day without clouds (July 13, 2017) was $7.11Wm^{-2}$ in comparison to the reference pyranometer. After the outdoor calibration of the pyranometer sensitivity based on these results, the RMSE of the observational data was $1.74Wm^{-2}$ on the same day. Periodic inspections are required because the decrease of sensitivity over time is inevitable in the pyranometer data produced at the observatory. The initial sensitivity after indoor calibration ($8.98{\mu}V{\cdot}(Wm^{-2})^{-1}$) is important, and the sensitivity after outdoor calibration ($8.90{\mu}V{\cdot}(Wm^{-2})^{-1})$ can be compared to the data at the Baseline Surface Radiation Network (BSRN) or can be used for various studies and daily applications.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.402-405
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• 2006

Radiometric calibration of optical image data is necessary to convert raw digital number (DN) value of each pixel into a physically meaningful measurement (radiance). To extract rather quantitative information regarding biophysical characteristics of the earth surface materials, radiometric calibration is often essential procedure. A sensor detects the radiation of sunlight interacted atmospheric constituents. Therefore, the amount of the energy reaching at the sensor is quite different from the initial amount reflected from the surface. To achieve the target reflectance after atmospheric correct, an initial step is to convert DN value to at-sensor radiance. A linear model, the simplest radiometric model, is applied to averaged spectral radiance for this conversion. This study purposes to analyze the sensitivity of several factors affecting on radiance for carrying out absolute radiometric calibration of panchromatic images from KOMPSAT2 launched at July, 2006. MODTRAN is used to calculate radiance at sensor and reflectance of target is measured by a portable spectro-radiometer at the same time the satellite is passing the target for the radiometric calibration. As using different contents of materials composing of atmosphere, the differences of radiance are investigated. Because the spectral sensitivity of panchromatic images of KOMPSAT2 ranges from 500 to 900 nm, the materials causing scattering in visible range are mainly considered to analyze the sensitivity. According to the verified sensitivity, direct measurement can be recommenced for absolute radiometric calibration.

• 전자공학회논문지SC
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• 제48권1호
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• pp.1-8
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• 2011

MR 센서에 의해 지구자기장의 세기를 측정하여 방위각을 결정하는 전자 Compass의 정밀도는 MR센서 및 OP-Amp.의 온도 Drift, DC Offset등 소자에 의한 오차, 측정주변 자성체에 의한 자기장의 왜곡, 및 Compass Tilt에 의한 오차 등의 영향을 받는다. 본 연구에서는 Set/Reset Pulse 방법에 의해 MR 센서 및 OP-Amp의 온도 Drift 및 DC Offset에 의한 오차를 해결하였고, 주변 자성체에 의한 자기장의 왜곡에 의한 오차를 Hard-Iron Calibration 루틴 수행에 의해 보상하였으며, Compass Tilt에 의한 오차를 Euler Rotational Equation에 의해 보상할 수 있는 3축 MR 센서 및 3축 Accelerometer를 기반으로 하는 전자 Compass 를 설계하였다. 특히 이와 샅이 설계한 전자 Compass를 가지고 3측 MR 센서의 서로 다른 Sensitivity와 OP-Amp.의 서로 다른 Gain등을 규준화하기 위한 Sensitivity Calibration 루틴 수행 시 Tilt의 발생으로 야기되는 오차를 정량적으로 분석하였으며, 이를 바탕으로 $1^{\circ}$정도(精度) Compass를 설계할 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.1059-1060
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• 2010

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.387-393
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• 2004

General purpose of cylindrical capacitive displacement sensor(CCS) is measuring run-out motion and deflection of rotor. If CCS has narrow sensing range, its sensitivity coefficients must be calibrated precisely. And x, y component of CCS output can be coupled. In this research, CCS calibration procedure is automated with automatic calibration program and PC-controlled stage. And, coupled-terms of CCS signals were removed and the errors between measured position and mapped CCS signal were reduced obviously by sensitivity matrix that linearly.

• Tribology and Lubricants
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• 제29권2호
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• pp.91-97
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• 2013

Quantifying the nanoscale force between the atomic force microscopy (AFM) probe of a force-sensing cantilever and the sample is one of the challenges faced by AFM researchers. The normal force calibration is straightforward; however, the lateral force is complicated due to the twisting motion of the cantilever. Force measurement in a liquid environment is often needed for biological applications; however, calibrating the force of the AFM probes for those applications is more difficult owing to the limitations of conventional calibration methods. In this work, an accurate nondestructive lateral force calibration method using multiple pivot loading was proposed for liquid environment. The torque sensitivity at the location of the integrated probe was extrapolated based on accurately measured torque sensitivities across the cantilever width along a few cantilever lengths. The uncertainty of the torque sensitivity at the location of the integrated tip was about 13%, which is significantly smaller than those for other calibration methods in a liquid environment.

• 한국정밀공학회지
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• 제28권5호
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• pp.585-590
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• 2011

Accelerometers have been exploited widely in various fields from monitoring vibration of precision machines to detecting an earthquake wave. The precision calibration of the accelerometers is required to maintain the measurement reliability when measuring the vibration of objects with accelerometers for modal analysis. Among evaluation factors for determining sensitivity of accelerometers, phase delay term should be also considered for accurate calibration. In this paper, a new calibration system of accelerometers capable of measuring phase delay as well as magnitude of its sensitivity was proposed and realized in the frequency range of 20 Hz to 5 kHz.

• 대한기계학회논문집
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• 제18권4호
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• pp.977-985
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• 1994

New computer-aided calibration methods for the hot-wire and split film probes are presented. The proposed modified king's law takes into account instantaneous flow angle as well as the variation of calibration coefficients due to the total velocity magnitude change. It is found that the look-up table method has many advantages with respect to the accuracy on data and reducing run time for calibration over other conventional methods. In order to investigate the local sensitivity of the static calibration, a dynamic calibration procedure is also carried out.

• 제어로봇시스템학회논문지
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• 제14권11호
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• pp.1174-1179
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• 2008

Many modeling and calibration methods have been developed to analyze and design the biological wastewater treatment process. For the systematic use of activated sludge model (ASM) in a real treatment process, a most important step in this usage is a calibration which can find a key parameter set of ASM, which depends on the microorganism communities and the process conditions of the plants. In this paper, a standardized calibration protocol of the ASM model is developed. First, a weighted effluent quality index(WEQI) is suggested far a calibration protocol. Second, the most sensitive parameter set is determined by a sensitive analysis based on WEQI and then a parameter optimization method are used for a systematic calibration of key parameters. The proposed method is applied to a calibration problems of the single carbon removal process. The results of the sensitivity analysis and parameter estimation based on a WEQI shows a quite reasonable parameter set and precisely estimated parameters, which can improve the quality and the efficiency of the modeling and the prediction of ASM model. Moreover, it can be used for a calibration scheme of other biological processes, such as sequence batch reactor, anaerobic digestion process with a dedicated methodology.

• 환경영향평가
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• 제20권3호
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• pp.357-365
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• 2011

The QUAL2K has the same basic characteristics as the QUAL2E model, which has been widely used in stream water quality modeling; in QUAL2K, however, various functions are supplemented. The QUAL2Kw model uses a genetic algorithm(GA) for automatic calibration of QUAL2K, and it can search for optimum water quality parameters efficiently using the calculation results of the model. The QUAL2Kw model was applied to the Gangneung Namdaecheon River on the east side of the Korean Peninsula. Because of the effluents from the urban area, the middle and lower parts of the river are more polluted than the upper parts. Moreover, the hydraulic characteristics differ between the lower and upper parts of rivers. Thus, the river reaches were divided into seven parts, auto-calibration for the multiple reaches was performed using the function of the user-defined automatic calibration of the rates worksheets. Because GA parameters affect the optimal solution of the model, the impact of the GA parameters used in QUAL2Kw on the fitness of the model was analyzed. Sensitivity analysis of various factors, such as population size, crossover probability, crossover mode, strategy for mutation and elitism, mutation rate, and reproduction plan, were performed. Using the results of this sensitivity analysis, the optimum GA parameters were selected to achieve the best fitness value.