Abstract: The present invention is embodied in a tensiometer apparatus and process that employs novel techniques for performing the required routine service operation of refilling a sealable measurement chamber of the apparatus with liquid from a reservoir using a novel, piston-type, “jet-action” plunger mechanism. These novel techniques result in a tensiometer which is easier to use, requires no tools for assembly or replacement of parts, and is easier and lower cost to manufacture and maintain. These novel techniques also result in a tensiometer which has improved measurement sensitivity and accuracy, higher reliability and a longer operating lifetime than conventional tensiometers.

Abstract: A waveguide assembly adapted for use with a time domain reflectrometry device for use in measuring the moisture content in soils and other mediums. A waveguide assembly comprised of a plurality of waveguide conductors (probes) for insertion into the soil are connected to a coaxial cable. An electronic stepped pulse travels through the coaxial cable and, due to an impedance mismatch where the coaxial cable and the waveguide assembly are joined, a downgoing beginning reference wave or reflection is produced. The beginning reference wave provides a starting point for measuring the accumulated time delay as the electronic pulse continues to travel through the waveguide assembly. An ending reflection wave is created as the electronic pulse reaches the end of the waveguide assembly and transmits into the surrounding soil.

Abstract: A waveguide assembly adapted for use with a time domain reflectrometry device for use in measuring the moisture content in soils and other mediums. A waveguide assembly comprised of a plurality of waveguide conductors (probes) for insertion into the soil are connected to a coaxial cable. An electronic stepped pulse travels through the coaxial cable and, due to an impedance mismatch where the coaxial cable and the waveguide assembly are joined, a downgoing beginning reference wave or reflection is produced. The beginning reference wave provides a starting point for measuring the accumulated time delay as the electronic pulse continues to travel through the waveguide assembly. An ending reflection wave is created as the electronic pulse reaches the end of the waveguide assembly and transmits into the surrounding soil.

Abstract: A portable tensiometer for measuring the moisture content of soil, including an elongated housing tube having a hollow porous tip mounted thereon for insertion in the soil, and a hollow handle element having a vacuum gauge secured to one end and a cylinder defining a chamber of adjustable volume at the other end. Capillary tubing, which connects the interior of the porous tip to the adjustable-volume chamber and to the vacuum gauge to form a sealed, normally water-filled system, and the use of a minimal volume of water in the instrument minimizes errors due to changes in temperature to which the instrument is subjected.