Balanced two-conductor time domain reflectometer

• Main Author: ANDERSON SCOTT K
• Format: Patent
• Language: English
• Published: 09.10.2012
• Subjects: MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

The described apparatus and methods use Time Domain Reflectometry (TDR) to determine the absolute volumetric moisture content of various media. The effects of dispersion caused by conductive and dielectric properties of the medium on the waveform are extrapolated by detecting the bulk propagation time and the slope of the distorted transition of the characteristic reflected waveform. Fast transitions are injected by a differential step function generator into a two-conductor waveguide, which is immersed in soil or other medium of interest. Unlike previous single-ended TDR systems, a differential digitizer senses the probes. Timing control between the two digitizers is critical. Use of an integrated fully differential system eliminates the need for a coaxial cable and an associated balancing transformer, or balun. This enables a two-conductor probe that is more easily inserted into soil, rather than requiring three conductors. Non-conductive probe tips may be pointed to facilitate insertion without causing measurement ambiguity.