用于土壤水分检测的inside-out型磁共振传感器优化
首发时间:2020-03-31
摘要:inside-out结构的磁共振传感器已成为土壤水分检测领域的新热点,在土壤水分检测时通常采取对待测土壤采样和非采样两种方式,显而易见非采样的方法更快速,而且保护了土壤本身结构,这对评估土壤物理结构很重要。目前已有的inside-out结构磁共振传感器中,在非采样测量方式的单边型结构仅能测量土壤浅层,对较深层次(1cm-10cm)土壤则无能为力,所以适应打孔测量的哑铃型结构、空心Jackson型结构更具有实用性。然而在国内缺少对相关传感器的优化设计和横向对比,使得在土壤水分测量领域磁共振传感器的推广普及受阻。本文优化和对比研究了哑铃型结构和空心Jackson型结构两种磁共振传感器的性能,首先,利用坐标搜索的非导数优化方法在相同的实际工程限制条件下,以在目标区域建立均匀磁场为目标优化设计了两款传感器的磁体结构;然后,在磁体产生磁场的基础上以信噪比为标准,再次利用坐标搜索法优化设计了射频线圈获得了传感器的最大信噪比;最后,通过对比量化的信噪比得出哑铃型传感器具有更高信噪比和性能。
关键词: 超低场磁共振 inside-out传感器 坐标搜索 土壤水分检测
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Optimization of inside-out magnetic resonance sensors for soil moisture detection
Abstract:The magnetic resonance sensor with inside-out structure has become a new hotspot to measure soil moisture. There are two common-used approaches of the measurement, sampling and non-sampling. Obviously, the non-sampling method is more convenient and better for soil structure detection, which is very important for accurate evaluation of the soil physical structure. Among the existing inside-out structural magnetic resonance sensors, conventional non-sampling unilateral structure can only measure the shallow layer of the soil, but it is powerless for the deeper layer (1cm-10cm) of the soil. So the dumbbell and the Jackson structure that are suitable for the hole drilling measurement are more practical. However, the lack of optimal design and horizontal comparison of related sensors in China has hindered wider application of magnetic resonance sensors on soil moisture measurement. This article optimized and compared the structure and performance of both dumbbell type and Jackson type sensors. First, the non-derivative optimization method of coordinate search is used to optimize the magnet structure of each sensor, in order to establish a uniform magnetic field in the target area under the same practical engineering constraints. Then, based on the magnetic field generated by the magnet, the signal to noise ratio (SNR) is taken as the standard, and the maximum SNR of the sensor is obtained by the new-designed using the coordinate search method. Finally, it is concluded that the dumbbell sensor has higher signal-to-noise ratio and performance by comparing the quantized signal-to-noise ratio.
Keywords: ultra-low field magnetic resonance Inside-out sensor Coordinate search Soil moisture detection.
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