A Study Of The Measurement Method Of Direct Radiation Sunshine Duration

The sunshine duration measurement is an important component of the solar radiation distribution measuring. Observing the sunshine duration has an important significance on the understanding of direct solar radiation changing, weather monitoring, analyzing and forecasting. It also can help guide agricultural production, exploit solar energy, architectural layout and monitor environmental. Currently the instrument to measure sunshine is sunshine recorder. How to improve the accuracy of sunshine has a very important significance for the accurate measurement of sunshine duration.The sunshine duration is defined as a period of time that the sunshine direct irradiance are more than120W/m2.97%of the solar radiation energy is located in0.3～3.0μm. However, the spectrum response range of most sunshine recorder is during0.2～1.1μm, meanwhile, the wavelength range of most optoelectronic device is not flat.In view of the above two problems, a new type of sunshine detector based on direct radiation measurement is designed in this paper. Due to the material constraints of a single sensor, it is difficult to satisfy the requirement of the spectral response for the sunshine recorder. So, then based on the multi-sensor data fusion theory, using three sensors to measure ultraviolet, visible light and infrared band, then fusing the signals, which can make up the defect of single sensor measurement.After investigating and selecting amount of sensors, the sensor of ZnS material is used in the UV bands, and pyroelectric infrared detectors is selected to measure infrared spectral bands. According to the problem that the response spectral curve of visible light sensor is not flat, color-sensitive diodes are used on the light intensity measurement to get the illumination intensity of the red, green and blue three colorful lights emitted by the tungsten lamp respectively. A weighted sum of the three groups of detecting signals has been gotten in accordance with the principles of the method of least squares, and a novel visible light measurement system is designed with the error analysis.The hardware device of this system can be divided into two parts:optical system and signal processing system. The optical system consists of light tube, lens, the aperture and the sensor. Through a combination of lens and the aperture stop, let the solid angle within a specific light into the optical path of the next section, eventually reaching the detector, the detector turn light signals into electrical signals. The signal processing system is divided into the preamplifier circuit, signal integration circuit, the threshold judgment and timing circuit system. The photoelectric signal effectively amplifies by the preamplifier circuit in photovoltaic mode, thus improves the signal-to-noise ratio of the system, so the noise influence on the effective signal is low. Signal scaling operation circuit integration is based on multiple relationships between different resistances, adjustable by adjusting potentiometer, then the weighting of multi-channel signal calculated. The threshold judging circuit is based on the definition of sunshine duration. The optical signal radiation density judges the received sensor whether reaches the threshold120W/m2or not. When it reaches the threshold, the timer will start counting, if it is below the threshold, the timer will not count until a threshold is reached.At last, the recorder is completed. In this paper, based on the multi-sensor data fusion theory, the solar radiation is measured by multiple sensors, effectively solves the limited spectral response of radiation sensors. Meanwhile, the wide spectrum measurement provides a new way of thinking and broadens the outlook of solar radiation measurement.