Patent ID: 8607618

Claim:
An electronic level sensor and timer-based falling head soil permeameter for measuring precisely the permeability of a soil sample, said permeameter comprising: a glass burette ( 7 ) having an interior, an inlet, and an output; upper and lower liquid level sensor assemblies ( 8 ) positioned for sensing the presence or absence of liquid in the interior of said burette, said sensors having a predetermined vertical separation from one another; a chamber assembly of three vertically stacked chambers, said assembly including: a top, vertically oriented tubular chamber ( 5 ) having an internal radius, a top chamber inlet coupled to said burette output to receive water from said burette, and a top chamber outlet; a middle, vertically oriented tubular chamber ( 4 ) having an internal radius which is at least approximately the same as the internal radius of the top tubular chamber, a middle chamber input coupled to receive water from said top chamber outlet, and a middle chamber outlet; wherein said middle chamber ( 4 ) holds a soil sample; and a bottom chamber ( 3 ) having a bottom chamber input to receive water from said middle chamber output and a bottom chamber outlet; wherein said bottom chamber ( 3 ) has an upper cylindrical portion having a radius which is at least approximately the same as the internal radius of the top tubular chamber, and a lower portion having a radius smaller than the radius of the upper cylindrical portion; wherein said top chamber discharges water only through said top chamber outlet; wherein said middle chamber discharges water only through said middle chamber outlet; wherein at least said top and middle chambers are made of copper; a first, perforated Teflon disk located in said top chamber ( 5 ) and supported on the soil sample for separating said top and middle chambers; a second, perforated Teflon disk seated in said upper cylindrical portion of said bottom chamber ( 3 ) for separating said middle and bottom chambers; and wherein said upper, middle, and bottom chambers may be disassembled from one another; wherein said sensor assemblies each comprise a photo sensor, an LED, and a clear plastic dome positioned relative to one another such that, when air covers the dome, light emitted by the LED is directed substantially towards the photo sensor so that the photo sensor is on; and positioned such that, when water covers the dome, some of the light emitted by the LED which would otherwise reach the photo sensor escapes into the liquid such that the photo sensor turns off; and an electronic timer unit ( 10 ) electrically coupled to said sensors in a manner such that a liquid level falling below the upper sensor assembly starts said timer unit, and such that a liquid level falling below the lower sensor assembly stops said timer.