Combined Penetrometer and Standing Wave Ratio Probe to Measure Compactness and Moisture Content of Soils

Abstract

Compactness and moisture content are important and mutually influential soil parameters that affect plant growth, nutrient absorption, and nutrient transportation. To simultaneously measure these two parameters, we developed a combined penetrometer standing wave ratio (PSWR) probe; acceleration measurement was facilitated to eliminate the error caused by varying penetration speeds. The performance of the instrument was analyzed and verified through laboratory and field measurements. The cone-index measurements from an SC-900 sensor and the moisture content calculated by the drying method and a TDR sensor were used to evaluate the performance. The results prove that acceleration compensations can improve the accuracy of cone-index measurements. Further, the sensitive range of the PSWR probe was the area a 10 cm diameter. The linear-fitting coefficient of output voltage and volumetric moisture content exceeded 0.96, and the output was stable; therefore, the moisture content measurements using the PSWR probe were validated. Furthermore, the accuracy and stability of measurements using the PSWR probe and a TDR sensor were similar. The field-measurement results agreed with the results from the drying method, and satisfied the practical implementation requirements. Conclusively, the validated efficiency and the cost-effective stainless-steel structure of the probe render it suitable for practical applications.

Miniature Noninvasive Sensor Based on Impedance-Change Detection in Branches for Measuring Branch Ice Content in Overwintering Woody Plants

“…When the high-frequency electromagnetic wave reaches the probe along the coaxial transmission line, the electromagnetic wave at the bimetallic ring probe changes in the transmission process, owing to the change in plant impedance between the bimetallic ring probes; the magnetic field medium changes with it, which causes the reflected electromagnetic wave to change, which in turn causes the two ends of the coaxial transmission line. The change in potential difference between the two ends of the transmission line can be found by measuring the change in voltage between ends to establish the change in the electromagnetic field at the outer edge of the probe, and thus measure the branch tissue impedance at the probe [ 33 , 34 , 35 ]. To improve the resolution of the potential difference between the two ends of the coaxial transmission line, the voltage difference between the two ends must perform signal amplification processing, and the final voltage obtained is: where is the potential difference between the two ends of the coaxial transmission line; is the amplification; is the excitation signal source amplitude; is the impedance at the probe at the measurement electrode; is the coaxial transmission line impedance (50 Ω); , , are fixed values; is only related to ; and the size of is determined by the branch impedance and electrode impedance.…”

Free space traveling–standing wave attenuation method for microwave sensing of grain moisture content

“…26,27 Normally a slotted line with movable probe or a movable short circuit and a fixed probe are used to determine the standing wave ratio of the standing wave induced by reflection at the specimen cell. 28,29 Restricted to the structure of the measuring device, the sample needs to be placed in a specific waveguide cavity or in close contact with the measuring probe, which cannot be measured for granular stacking samples in free space.…”