Improved Calibration of Frequency Domain Reflectometry Probes for Volumetric Water Content Measurements of Three Media

2011 ◽  
Vol 55 (1) ◽  
pp. 51-60
Author(s):  
Y. Ting ◽  
C. Chen
Keyword(s):  
Water Content ◽  
Frequency Domain ◽  
Volumetric Water Content ◽  
Frequency Domain Reflectometry

Measuring Water Content Characteristics by Using Frequency Domain Reflectometry Sensor in Coconut Coir Substrate

2014 ◽  
Vol 23 (2) ◽  
pp. 158-166 ◽  
Author(s):  
Sung Tae Park ◽  
태 박성 ◽  
Geum Hyang Jung ◽  
Hyung Joo Yoo ◽  
Eun-Young Choi ◽  
...  
Keyword(s):  
Water Content ◽  
Frequency Domain ◽  
Frequency Domain Reflectometry ◽  
Coconut Coir ◽  
Content Characteristics

Measuring duff moisture content in the field using a portable meter sensitive to dielectric permittivity

2004 ◽  
Vol 13 (3) ◽  
pp. 343 ◽  
Author(s):  
P. R. Robichaud ◽  
D. S. Gasvoda ◽  
R. D. Hungerford ◽  
J. Bilskie ◽  
L. E. Ashmun ◽  
...  
Keyword(s):  
Dielectric Permittivity ◽  
Water Content ◽  
Forest Cover ◽  
Volumetric Water Content ◽  
Moisture Meter ◽  
Sample Chamber ◽  
Frequency Domain Reflectometry ◽  
Forest Cover Types ◽  
Gravimetric Water Content ◽  
Best Fit

Duff water content is an important consideration for fire managers when determining favourable timing for prescribed fire ignition. The duff consumption during burning depends largely on the duff water content at the time of ignition. A portable duff moisture meter was developed for real-time water content measurements of non-homogenous material such as forest duff. Using circuitry developed from time and frequency domain reflectometry (TDR and FDR) technologies, this sensor measures a change in frequency that is responsive to the dielectric permittivity of the duff material placed in a sample chamber and compressed. Duff samples from four forest cover types—Douglas fir, larch, lodgepole pine and spruce/alpine fir—were used to calibrate the frequency output to volumetric water content. A second-order polynomial (R2 = 0.97) provides the best fit of the data to volumetric water content. The accuracy of the duff moisture meter is ±1.5% at 30% volumetric water content and ±4% at 60% volumetric water content. The volumetric water content can readily be converted to gravimetric water content, which is used more frequently by fire managers and as an input to predictive models of duff consumption.

scholarly journals Estimation of the daily water consumption by maize under Atlantic climatic conditions (A Coruña, NW Spain) using Frequency Domain Reflectometry – a case study

2012 ◽  
Vol 12 (3) ◽  
pp. 709-714 ◽  
Author(s):  
R. M. Mestas-Valero ◽  
J. M. Mirás-Avalos ◽  
E. Vidal-Vázquez
Keyword(s):  
Water Content ◽  
Frequency Domain ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Consumption ◽  
Climatic Variables ◽  
Accurate Estimation ◽  
Frequency Domain Reflectometry ◽  
Daily Water ◽  
Daily Water Consumption

Abstract. Climatic variables and soil present a high spatio-temporal variability. Evapotranspiration estimations based on climatic variables may be inadequate for assessing soil water content in the root-influenced zone and/or soil water consumption by plants. Other methods may provide better estimates of this water consumption. The aim of this study was to quantify the soil moisture dynamics in the root-influenced zone and to assess the daily water consumption by the crop using Frequency Domain Reflectometry (FDR). The studied site is located in A Coruña (Spain). The study was carried out from June to October in 2008 and 2009, in a maize (Zea mays, L.) field on a silt-clay textured soil. Evapotranspiration was estimated by the Penman-Monteith equation using meteorological data from a station located on the experimental site. Soil water content in the root-influenced zone (0–60 cm depth) was hourly monitored each 20 cm (0–20 cm, 20–40 cm, and 40–60 cm) using FDR. Evaluations were performed on days with slight or no rainfall. During the study period, the magnitude of the diurnal soil water loss was more evident in the first layer (0–20 cm depth) and less important in the subsequent soil layers. The greatest consumption occurred between 14 and 19 h, up to 53.64% of the total. Overall, daily water consumption increased significantly with soil water content (p-value < 0.001). In general, water losses from the 0–20 cm soil layer were greater than in subsoil horizons due to maize water-uptake and evaporation. In contrast, water content in the deepest part of the soil profile was close to saturation, even on the driest days of the studied period. Evapotranspiration overestimate maize water requirements as its values were greater than those measured with the probe. In conclusion, FDR allows a more accurate estimation of the soil water balance. Therefore, monitoring soil water content would be useful in the assessment of saturation risks or water stress (drought), thus aiding in the decision making, for instance, in irrigation management. Results from this study may help to improve irrigation practices in humid zones.

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