Abstract: Digitized images of the propagated waveforms returned by Time-Domain (TD) sensors reveal the effects of bound water in soil samples, causing errors in the volumetric water content reported for samples due to soil type. Pattern analysis yields not only correct volumetric water content values but also the soil type from which the waveform was taken. Collection and analysis of waveforms from soils having precisely known properties yield computer-generated algorithms to improve the accuracy and number of reporting variables for integrated TD sensors. These algorithms can be deployed in the Cloud for external analysis, or can be incorporated within the sensor to report highly accurate readings of water content, conductivity and soil type under all conditions of these variables with no interpretive burden placed on the user of the sensor. Machine learning algorithms are intended to externally augment data measured by these sensors, or can be added to similar sensors.

Abstract: 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.

Abstract: An absolute moisture sensor is coupled to a controller circuit with the combination being integrated into a single device as a moisture-activated switch. The resultant switch is coupled in series with a power control line of a moisture-controlling device and can be placed within the medium for which moisture is to be controlled. In one typical use, the switch is buried in soil for control of valves that supply irrigation water. Since the moisture sensor is selected to provide an absolute reading of moisture, the switch programs itself when power from an external source is first applied. A communication protocol provides for readout of sensor values and allows for a remote reset of the controller.

Abstract: A combination of frequency and time division multiplexed signals communicates using bursts of higher frequency sinusoidal waves superimposed upon the alternating current in a two-wire power distribution network. A synchronization pattern precedes data, all bursts having the same frequency to overcome problems caused by varying reactances, and all bursts being confined within negative half-cycles of the AC power. Such networks minimize the amount of wire needed to connect large numbers of devices to a common controller while covering large distances, and requiring no particular connection pattern or terminations, whether near the surface, above ground, or in deep earth wells. In an irrigation system they accommodate at once solenoid valves and distributed environmental sensors. Landscape changes that would otherwise require new wiring to accommodate new irrigation zones are facilitated by merely tapping into the two-wire communications lines at the nearest accessible point.

Abstract: Narrow pulses transmitted wirelessly from a transmitting antenna to a receiving antenna are used to measure the electrical permittivity of the medium of interest between the two antennas. Timing signals are transmitted along a shielded transmission line coincident with the wireless transmission through the medium. The received waveform is digitized in the time domain and analyzed to determine the propagation time. The effects of dispersion caused by the conductive and dielectric properties of the medium on the transmitted waveform are overcome through analysis of the digitized waveform, resulting in an accurate measurement of the propagation time and thus the permittivity of the medium, from which volumetric moisture content may be derived.

Abstract: Narrow pulses transmitted wirelessly from a transmitting antenna to a receiving antenna are used to measure the electrical permittivity of the medium of interest between the two antennas. Timing signals are transmitted along a shielded transmission line coincident with the wireless transmission through the medium. The received waveform is digitized in the time domain and analyzed to determine the propagation time. The effects of dispersion caused by the conductive and dielectric properties of the medium on the transmitted waveform are overcome through analysis of the digitized waveform, resulting in an accurate measurement of the propagation time and thus the permittivity of the medium, from which volumetric moisture content may be derived.

Abstract: Methods and apparatuses are described for detecting volumetric moisture content and conductivity in various media based on a time-domain reflectometry (TDR) system wherein successive fast transitions are injected into a transmission line immersed in a medium of interest, and a characteristic received waveform is digitized and analyzed by continuously sampling multiple received waveforms at short time intervals. One method transmits a timing signal along a shielded transmission line while a coincident signal is transmitted through the medium of interest. Another method propagates the waveform along a transmission line, that may be either shorted or open-ended, and observes a reflected, rather than transmitted, waveform with a receiver connected to the same end of the transmission line as the transmitter.

Abstract: 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.

Abstract: 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. 09/945528. As in patent application Ser. No. 09/945528, successive square waves are generated and transmitted on a transmission line through a medium of interest, and a characteristic received waveform is digitized and analyzed by continuously sampling multiple received waveforms at short time intervals. Unlike the former system, the system in this disclosure does not propagate the waveform along a transmission line to a receiver at the other end of the line, but uses a reflected wave approach in which the waveform propagates down a shorted or open ended transmission line and reflects back to a receiver connected to the same end of the line as the transmitter. The effects of dispersion caused by the conductive and dielectric properties of the medium on the waveform sent on the transmission line are extrapolated.

Abstract: Methods and apparatuses are described for detecting volumetric moisture content and conductivity in various media based on a time-domain reflectometry (TDR) system wherein successive fast transitions are injected into a transmission line immersed in a medium of interest, and a characteristic received waveform is digitized and analyzed by continuously sampling multiple received waveforms at short time intervals. One method transmits a timing signal along a shielded transmission line while a coincident signal is transmitted through the medium of interest. Another method propagates the waveform along a transmission line, that may be either shorted or open-ended, and observes a reflected, rather than transmitted, waveform with a receiver connected to the same end of the transmission line as the transmitter.

Abstract: A method of sensing moisture based on propagation-delay provides absolute readings of volumetric water content in a moisture-bearing medium without calibrating the sensor or its readings for the conductivity or temperature of the medium. A fast transition is launched on a transmission line that is immersed in the medium to be measured. The amplitude of the resultant waveform is analyzed at precise, programmable time increments by using a high-speed latching comparator. Firmware in a controlling microprocessor facilitates the successive reconstruction of the significant characteristics of the returning waveform. The microprocessor analyzes these characteristics to provide an accurate determination of propagation delay and conductivity, even for severely distorted waveforms. The moisture content of the medium is derived from the propagation delay.