| 摘要 |
A propagation-delay-based moisture sensor is disclosed that is capable of providing absolute readings of volumetric water content in a moisture-bearing medium without the need to calibrate the sensor or readings for the conductivity or temperature of the medium. It does so by launching a step transition on a transmission line that is everywhere in contact with the measured medium and that returns the waveform to a high-speed latching comparator wherein the amplitude of the returning waveform is analyzed at precise, programmable time increments. Firmware means in a controlling microprocessor facilitate the successive reconstruction of the significant characteristics of the returning waveform. Analysis of these characteristics by the microprocessor leads to an accurate determination of propagation delay even for severely distorted waveforms. From the propagation delay the moisture content of the medium is derived. A supplemental feature is the derivation of medium conductivity from the characteristics of the successively-measured waveform.
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