In agricultural field, compact sensors that can measure both water content and electric conductivity are needed. Focusing on the fact that water content and conductivity depend on soil impedance, our group has been developing a new compact and noise-resistant driving circuit that measured soil impedance by detecting transient characteristics of the voltage obtained by injecting current through the soil and converting it to frequency information. In order to realize agricultural field measurements with sensors using this new driving circuit, it had been necessary to miniaturize the part that detected the output from the driving circuit, but it hadn't been achieved in our previous work. In this research, a microcomputer-based frequency counter was developed to downsize the system for on-site measurement. In general, there are two methods of frequency measurement: direct counting and reciprocal. The direct-counting method is suited for high-frequency measurements, while the reciprocal method is suited for low-frequency measurements. The developed frequency counter could measure with an error of 0.005% over the assumed frequency range by switching between those two measurement methods according to the measured frequency. Using this driving circuit and frequency counter, we measured the model soil and succeeded in capturing changes in water content as changes in impedance.

中文翻译：

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土壤含水量频率测量电路和电导率测量系统的开发，可检测土壤瞬态响应特性，便于现场测量

在农业领域，需要能够测量水分含量和电导率的紧凑型传感器。针对水分含量和电导率取决于土壤阻抗的事实，我们课题组一直在开发一种新型紧凑型抗噪声驱动电路，通过检测向土壤注入电流所获得的电压的瞬态特性并将其转换为测量土壤阻抗的方法。频率信息。为了利用这种新型驱动电路通过传感器实现农田测量，需要将检测驱动电路输出的部分小型化，但在我们之前的工作中尚未实现。在这项研究中，开发了一种基于微机的频率计数器，以缩小现场测量系统的尺寸。一般来说，频率测量有两种方法：直接计数法和倒数法。直接计数法适合高频测量，而倒数法适合低频测量。通过根据测量频率在这两种测量方法之间切换，开发的频率计数器可以在假定的频率范围内以 0.005% 的误差进行测量。使用该驱动电路和频率计数器，我们测量了模型土壤，并成功地将含水量的变化捕获为阻抗的变化。根据测量频率在这两种测量方法之间切换，可在假定频率范围内实现 005% 的测量。使用该驱动电路和频率计数器，我们测量了模型土壤，并成功地将含水量的变化捕获为阻抗的变化。根据测量频率在这两种测量方法之间切换，可在假定频率范围内实现 005% 的测量。使用该驱动电路和频率计数器，我们测量了模型土壤，并成功地将含水量的变化捕获为阻抗的变化。