基质根区阻抗谱测量中补偿和耦合方法研究

根区阻抗谱技术可以很好地展现根区水分、生物量等动态变化。针对相邻激励策略下的基质根区100 Hz～2 MHz范围内阻抗谱测量中出现的问题,进行总结、分析,并提出了解决方法。进行了延长通道对测量的影响实验,分析对比了单端口网络和双端口网络补偿策略,实验结果表明,纯基质的测量,单端口网络补偿方法是最佳选择,其步骤简洁且补偿效果显著。通过延长电极长度,使自然条件下阻抗谱可被准确测量的含水率变化范围增大,电极由3 mm增长至8 mm时,适用的含水率范围从8. 35%增大至11. 27%,是原有含水率范围的1. 35倍,有效地减弱了含水率下降时对电极与基质耦合的影响。分析了不同电极长度下的数据差异以及电极几何参数的影响,结果表明,电极长度变化并未对数据的整体趋势变化造成显著影响。同时,对测量中高频时出现负电阻数据的原因进行了分析探讨。

Compensation and Coupling Methods in Impedance Spectroscopy Measurement for Substrate Root Zone

The root zone of plant provides a base for use of nutrients and water resources and supports the plant, in which the interaction between root and medium affects the uptake of water and nutrients. The technology of impedance spectroscopy can well reflect the dynamic change of water content and root biomass in the root zone. However, there are many factors that limit the application scenarios which can be measured. The research was focused on the problems encountered in the impedance spectroscopy measurement for the substrate root zone under the adjacent excitation strategy within the range of 100Hz~2MHz.The solutions were provided and compared. For the effect of the extended fixtures, compensation methods of single-port network and dual-port network were calculated and analyzed. The experimental results supported that the selection of single-port network compensation method was a better strategy for pure substrate impedance measurement, whose process was simple and the compensation result was remarkable. Through lengthening the electrodes, the range of water content in substrate root zone, that ensure the impedance spectroscopy can be accurately measured under natural dry condition, was increased to 11.27% at 8mm condition from 8.35% at 3mm, which was 1.35 times of the original range and effectively attenuated the effect of the root zone water content decrease on electrode coupling. And the data differences under different electrode lengths and effect of variations in electrode geometry were analyzed. The results showed that the change in electrode length had no significant impact on the overall trend of the impedance spectroscopy data. Furthermore, the reasons why the negative resistance data appeared in the high frequency range were presented and analyzed. These analysis and resolutions of measurement compensation and coupling problems would provide references for scientific researchers in the impedance study for the root zone.