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Conduction type soil matric potential sensor

  • US 4,216,789 A
  • Filed: 10/11/1977
  • Issued: 08/12/1980
  • Est. Priority Date: 01/17/1977
  • Status: Expired due to Term
First Claim
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1. In a matric potential sensor, the combination comprising(a) a housing including a porous wall adapted to be located underground,(b) spaced electrodes carried in the housing to be coupled to a source of electrical current, and(c) granular material located to pass electrical current within the housing and between the electrodes so that the current flow will vary as a function of the moisture content of the granular material, said content adapted to vary as a function of the matric potential of the soil surrounding the housing in response to moisture transmission through the porous housing into the surrounding soil,(d) said sensor being located underground, and including a second and like sensor located in communication with irrigation water, and whose resistance varies as a function of exposure to moisture associated with said irrigation water, and electrical circuit means connected with said sensors to provide a comparison of the electrical resistances of said sensor, whereby the supply of irrigation water may be contolled as a consequence of said comparison.

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