Conduction type soil matric potential sensor

摘要

A matric potential sensor comprisesPP(a) a housing including a porous wall adapted to be located underground, P P(b) spaced metal plates carried in the housing to be coupled to a source of electrical current, andPP(c) granular material located to pass electrical current within the housing and between the plates 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.PP Special circuitry adapts the sensor for use with a solenoid type irrigation valve controller.