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United States Department of Agriculture

Agricultural Research Service

Title: Soil moisture sensor
See also: US Patent Office Full Record

Plains Area
  Lubbock, Texas

Patent Number: 7135871
Docket Number: 3805
Serial Number: 11304285
Date Patented: 11/14/2006


Summary: The moisture content of soil may be determined using a swept-frequency microwave-based process and device. The process includes the steps of: producing a primary microwave signal with a varying frequency, splitting the primary signal to provide first and second microwave signals, which first signal is transmitted through an electric conductor in the soil where it will be delayed in proportion to the dielectric constant of the soil, while the second signal provides an internal reference signal, receiving a third signal which includes the first signal after it has passed through the electrical conductor, mixing the third signal together with the second signal, generating a mixed signal, filtering the mixed signal to remove upper side-band interference signals, generating a filtered-mixed signal, measuring the frequency of the filtered-mixed signal and calculating the moisture content of the soil.

Patent Status: Patent issued on November 14, 2006. Link at USPTO filed under patent title “Soil moisture sensor.”


Mathew G Pelletier
Cotton Production and Processing Research
ROUTE 3, BOX 215
LUBBOCK, TX, 79403
Phone: (806) 746-5353
Fax: (806) 744-4402


Last Modified: 10/1/2015
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