| 摘要 |
A method and apparatus for detecting volumetric moisture content and conductivity in various media based on the time-domain reflectometry (TDR) system disclosed in patent application Ser. No. 09/945,528. As in patent application Ser. No. 09/945,528, successive square waves are generated and transmitted on a transmission line through a medium of interest, and a characteristic received waveform is analyzed by continuously sampling multiple received waveforms at short time intervals. Unlike the former system, the system in this disclosure does not house the transmitting and receiving circuitry on the same circuit board, but uses a bistatic approach to separate transmitting and receiving modules. A timing signal is coincidentally sent with the transmitted waveform along a separate shielded transmission line. The effects of dispersion caused by the conductive and dielectric properties of the medium on the waveform sent on the unshielded transmission line are extrapolated. This is accomplished by detecting the bulk propagation time and the slope of the distorted rising edge of the characteristic received waveform. Absolute volumetric moisture percentage is inferred from propagation time, and absolute conductivity is inferred from the maximum slope value of the distorted rising edge of the characteristic received waveform.
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