Calibration of a waveguide sensor for measuring soil moisture

• Published in: IEEE transactions on geoscience and remote sensing 1990-09, Vol.28 (5), p.873-878
• Main Authors: Parchomchuk, P., Wallender, W.W., King, R.J.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Calibration; Dielectric measurements; Electromagnetic measurements; Fundamental and applied biological sciences. Psychology; Impedance; Moisture measurement; Physical properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Q measurement; Reflection; Soil measurements; Soil moisture; Soil science; Structure, texture, density, mechanical behavior. Heat and gas exchanges; Volume measurement
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/36.58976

An open-ended waveguide is calibrated for use as a soil moisture sensor. The calibration procedure models the waveguide as a microwave network and uses an optimization procedure to calculate network parameters which minimize errors between measured and calculated response curves. The test load is formed by terminating the waveguide with a two-layered sand profile whose top layer thickness is incrementally adjusted to vary the output load. The output impedance of the waveguide is approximated from intrinsic impedances of the wave propagation through layered media. This approximation produced excellent agreement between reflection responses calculated from the network calibration parameters and those observed for a wide range of output loads.< >