An improved soil moisture sensing device

摘要

The present specification discloses a soil mixture sensing device for sensing moisture levels in a particular soil area under surveillance, the device having a porous body (11) which in use is placed in the soil area under surveillance, the body (11) having at least two zones, a first one of said zones (11) having pore sizes that approximate a range of pores in typical soils, a second one of the zones (14) having pores arranged to be small enough to remain hydrated at matric tensions of the soil solution significantly above those which cause the first zone (11) to dehydrate, the first zone (11) containing a first electrode (12) and the second zone (14) containing a second electrode (16), each of which are paired with an electrode (17) common to both said zones (11) and (14) whereby, as the matric tension of the soil solution in the soil in the surveillance area increases, the pores within the first zone (11) progressively dehydrate causing electrical resistance between the first electrode and the common electrode (17) to progressively increase while the pores in the second zone (14) remain hydrated such that the electrical resistance between the second electrode (16) and the common electrode (17) changes only in response to conductivity of the soil solution in the pores of the second zone (14).