HR: 09:15h
AN: H21E-04    [Abstracts]
TI: Comparison of Seven Electromagnetic Water Content Sensors Commonly Used in Ecohydrological Studies
AU: * Blonquist, J M
EM: jmarkb@cc.usu.edu
AF: Utah State University, Dept. of Plants, Soils, and Biometeorology 4820 Old Main Hill, Logan, UT 84322-4820 United States
AU: Jones, S B
EM: stjones@cc.usu.edu
AF: Utah State University, Dept. of Plants, Soils, and Biometeorology 4820 Old Main Hill, Logan, UT 84322-4820 United States
AU: Robinson, D A
EM: darobinson@cc.usu.edu
AF: Utah State University, Dept. of Plants, Soils, and Biometeorology 4820 Old Main Hill, Logan, UT 84322-4820 United States
AB: Numerous electromagnetic (EM) sensing systems are available which employ permittivity estimates to infer soil water content, but a standard method for characterizing EM sensing system measurement capability has not been established. Our objective was to evaluate the measurement accuracy and range of seven different systems using readily available dielectric liquids. Sensor outputs of travel time or voltage were converted to real permittivity and compared to real permittivity measurements using a network analyzer. Using standard waveform analysis, three higher frequency broadband sensing systems deviated from the network analyzer by less than ± 3.0 real permittivity units across a real permittivity range of 13 to 79 in lossless liquids. Two lower frequency impedance sensing systems deviated from the network analyzer by less than ± 4.0 real permittivity units across a real permittivity range of 13 to 37 in the same media. For the higher frequency systems, imaginary permittivity values (due only to dielectric relaxation) of up to 15 resulted in real permittivity errors of ± 0.51, whereas electrical conductivity values up to 2 dS/m resulted in real permittivity errors of ± 2.7. Temperatures in the range of 5 to 40 °C resulted in errors of ± 4.9. For four lower frequency systems, dielectric relaxation, electrical conductivity and temperature effects resulted in real permittivity errors of up to ± 6.6, ± 111 and ± 3.3, respectively. These effects on measurement accuracy are to a large extent dependent on measurement frequency; with higher frequency sensing systems generally yielding better measurements.
DE: 1800 HYDROLOGY
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2005 Joint Assembly