Abstract: A method of determining the moisture content of material on a bobbin featuring a hollow core, the method comprising the steps of: (a) transmitting a plurality of microwaves substantially through a portion of the bobbin, such that the microwaves are transmitted microwaves; (b) receiving the transmitted microwaves such that the microwaves are received microwaves; (c) determining a phase shift and an attenuation from the received microwaves; (d) repeating steps (a) to (c) for at least a portion of the material on the bobbin, such that a plurality of phase shifts and a plurality of attentuations is obtained; (e) using at least one empirical factor selected from the group consisting of weight of the bobbin, temperature of the bobbin, shape of the bobbin and type of the material to correct the plurality of attenuations, producing a plurality of corrected attenuations; (f) calculating a raw moisture content of the material from the corrected attenuations; (g) correcting the plurality of phase shifts for an artefact

Abstract: A time domain reflectometry linear position sensing system having a transmission line with a helically wound inductor and a ground conductor. The transmission line includes a movable member that electrically connects with the ground member and which extends along the inductor from a first end a distance that depends on the position of an object whose position is being determined. A signal generator applies pulses between the first end and the ground conductor and a receiver receives reflections of those pulses. The delays between the applications of pulses and the receptions of reflections depend upon the position of the object. A position determining circuit determines the position of the object based upon the delays, beneficially by using sing-around. Beneficially, a third member extends a predetermined distance along the inductor from a second end. That third member provides a reference delay that can improve the system accuracy.

Abstract: An apparatus (50, 100, 150) for sensing a surface level (20) of fluid (12) includes a generally cylindrical central conductor (16, 102, 152) for connection to a pulse signal source (26) with a reduced diameter end (28, 104, 154) and an opposite end (24, 124, 168); a generally tubular outer conductor (14) concentric with the central conductor for connection to the pulse signal source and having one open end (32) adjacent the central conductor reduced diameter end and an opposite open end (18) adjacent the central conductor opposite end, the central conductor and the outer conductor forming a transmission line for pulse signals generated by the pulse signal source and a cavity (C) between an interior wall surface of the outer conductor and an exterior surface of the central conductor; a non-metallic seal (54) mounted at the outer conductor open end for sealing the cavity, the central conductor reduced diameter end extending through a central aperture (52) formed in the seal; a circuit board (58) for mounting th

Abstract: An apparatus is disclosed for testing concrete having an unknown water/cement ratio and an unknown compressive strength. The apparatus includes a transmitter assembly for transmitting microwave signals at one or more predetermined frequencies. A receiver assembly receives each microwave signal reflected from the concrete under test. The reflected microwave signals, together with the transmitted microwave signals, are used to determine a reflection coefficient magnitude for the particular microwave frequency. A processing unit uses the reflection coefficient magnitude to determine a value related to concrete strength. In one embodiment, the processing unit relies on a logarithmic function that correlates the reflection coefficient magnitude and a water/cement ratio. A value related to the compressive strength of the concrete can also be obtained using the value of the water/cement ratio or the value of the reflection coefficient magnitude.

Abstract: A method and apparatus for measuring in-place soil density and moisture content. A cylindrical cell is disclosed which may be used to measure the density and the dielectric constant of a soil sample placed within the cylindrical cell. Also disclosed is a multiple rod probe which is designed to contact spikes driven into the ground to measure the in-place dielectric constant of soil. The multiple rod probe includes adjustable studs which ensure complete contact with the spikes. Both measurements are performed using time domain reflectometry. The present invention develops equations for determining the density of the soil in-place from the measured dielectric constant of the soil in-place and the measured density and dielectric constant of the soil in the cylindrical cell.

Abstract: An apparatus and method for the moisture content measurement of compressible materials using pressure to firmly hold surface probes against the material to be measured. The apparatus uses moisture measurement circuitry employed in frequency domain impedance or time domain reflectometry devices to obtain moisture content readings from materials. These moisture content readings are based on the apparent dielectric constant of the measured material. Subsurface air voids or gaps found in loose, layered materials undesirably influence moisture measurement readings by reducing the apparent dielectric constant of the measured material. Pressure is supplied through the apparatus to the material in the proximity of the surface probes, thereby reducing air voids to enhance measurement accuracy. The apparatus and method are especially useful for compressible organic materials such as forest duff, hay and soil.

Abstract: A device utilizes micropower, impulse radar and time domain reflectometry to determine the dielectric constant of a fluid. An electrically conductive probe preferably in the form of a transmission line, is inserted at least partially into the fluid. The device includes a signal generator that generates an impulse signal that is propagated along the probe. The time that it takes for the signal to reach the end of the probe is determined. The time of travel of the signal along the probe is then used to determine the dielectric constant of the fluid.

Abstract: A system for detecting accretion of frazil ice on underwater gratings comses a pair of parallel electrically conductive bars mounted side-by-side, for disposition beneath a water surface and spaced from but proximate an underwater intake grating. The system further includes a coaxial transmission line connected at a first end to the pair of bars for extension from the bars upwardly above the water surface, and a time domain reflectometer disposed above the water surface for generating electromagnetic pulses and having a second end of the transmission line fixed thereto. The transmission line facilitates propagation of the pulses to the bars for further travel to distal ends of the bars, and back to the reflectometer. The reflectometer is adapted to compute pulse round trip travel time in the bars and to compute changes in the round trip travel time, from which can be determined absence, presence, and build-up of frazil ice on the bars, providing an indication of same on the grating.

Abstract: Slow wave, time-domain reflectometer based point level sensors and instruments. Such sensors and instruments include a transmission line having an inner conductor, an outer shield that extends over that inner conductor so as to define a gap between the inner conductor and the outer shield, a dielectric material that fills the gap, except at a point, thereby defining a space, and an access opening for enabling a material being sensed to fill the space when that material is present. According to the invention the dielectric material has a permittivity substantially different from the material being sensed. Further included are a pulse generator for generating pulses on the transmission line, and a processing unit for determining whether the material being sensed fills the space. Beneficially the inner conductor is helically wound around a core, creating a slow wave transmission line.

Abstract: Moisture sensing apparatus that uses slow wave transmission lines. Such transmission lines include a helically wound inner core, a surrounding outer conductor, and a moisture bearing material between the inner core and the outer conductor. Preferably, the transmission line includes a moisture barrier that separates the transmission line into a sealed dry section and a wet section which is in moisture communication with its environment. The moisture sensing apparatus further includes a source of electrical signals on the transmission line, and a moisture sensing circuit, operatively connected to the slow wave transmission line, which senses the moisture content of the moisture bearing material from the velocity of the impressed electrical signals on the slow wave transmission line. Preferably, the velocity of the impressed electrical signals is obtained indirectly using a sing-around measurement technique.

Abstract: A measurement device and a method for indicating the ratio of two or more substances having different dielectric constants which form a body of material is described. The measurement device comprises an oscillator (1), a transmission line (5) connected at one end to the oscillator (1) and a probe unit (7) connected to the other end of the transmission line (5). The oscillator (1) transmits an oscillating signal via the transmission line (5) to the probe unit (7), where the probe unit (7) contacts with the body of material. The difference in voltage amplitude between two points in the transmission line (5) is measured, and is indicative of the ratio of the two or more substances.

Abstract: A method and apparatus for measuring in-place soil density and moisture content. A cylindrical cell is disclosed which may be used to measure the density and the dielectric constant of a soil sample placed within the cylindrical cell. Also disclosed is a multiple rod probe which is designed to contact spikes driven into the ground to measure the in-place dielectric constant of soil. The multiple rod probe includes adjustable studs which ensure complete contact with the spikes. Both measurements are performed using time domain reflectometry. The present invention develops equations for determining the density of the soil in-place from the measured dielectric constant of the soil in-place and the measured density and dielectric constant of the soil in the cylindrical cell.

Abstract: A probe for use in time domain reflectometry includes a body having a conductive portion and an insulated portion. A conductive loop is provided having a first end and a second end. The first end is secured in the insulated portion of the body. The second end is secured in the conductive portion of the body, thereby shorting and grounding the conductive loop. An RF connector is provided for coupling the first end of the conductive loop to time domain reflectometry instrumentation.

Abstract: A probe (1) is used to measure the dielectric properties of rigid or semi-rigid materials (4), for example, works of art. The probe comprises an inner conductor and an outer, coaxial, conductor separated by a layer of insulator e.g. Teflon (TM). The probe is coupled to a network analyzer (11), which provides microwave frequency radiation which is transmitted by the probe onto the surface of the material where it is reflected back from the surface back down the probe to the analyzer, where it is analyzed to give measurements on the dielectric properties of the material. The probe typically has an outside diameter of around 0.86 mm, and because of its size allows measurements to be made, non-invasively, and in real time on small areas of material. The outside diameter can be made of the order of microns by selecting the frequency of the radiation, which allows measurements to be made in a sample of a semi-rigid material e.g. a layer of paint for depth profiling.

Abstract: Time Domain Reflectometry ("TDR") methods and apparatus for measuring propagation velocities of RF pulses to determine material liquid contents, moisture profiles, material levels and dielectric constants including: i) TDR probes and/or probe adaptors, including series averaging probes and multi-segment probes, all employing remotely operable, normally open, variable impedance devices such as diodes; ii) bias insertion and switching networks for rendering selected normally open variable impedance devices conductive one at a time to establish precise unambiguous timing markers T.sub.1 . . . T.sub.

Abstract: A sensor for use with time domain reflectometry systems to allow measurement of relative proportions of intermixed constituents having differing electrical permittivities contained in a fluid mixture. The sensor comprises a central primary electrode and a pair of adjacent outer secondary outer electrodes. The fluid mixture is located between the electrodes during sensing. A dielectric layer covers exposed sensing surfaces of the electrodes to electrically isolate the electrodes from the fluid mixture and to prevent dissipation of a time domain reflectometry signal propagated through the sensor.

Abstract: A monitor for measuring physical parameters of a slurry, utilizing microwave propagation within a waveguide, either in conduit or a storage facility. Switching circuitry and specially constructed waveguides are provided, which operate in combination to provide rapid, accurate measurement of such parameters as flow rate, and concentration of the slurry.

Abstract: Method and apparatus for making measurements on fluids related to their complex permeability are disclosed. A microwave probe is provided for exposure to the fluids. The probe can be non-intrusive or can also be positioned at the location where measurements are to be made. The impedance of the probe is determined, in part, by the complex dielectric constant of the fluids at the probe. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids. Multiple probes may be selectively positioned to monitor the behavior of the fluids including their flow rate. Fluids may be identified as between two or more different fluids as well as multiple phases of the same fluid based on differences between their complex permittivities.

Abstract: The measurement of moisture content in granular materials is ordinarily a difficult measurement to make. The invention of this application sets forth a new method and apparatus for measuring moisture content in a wide variety of materials by means of application of an apparatus that makes measurement of moisture content independent of density of the material measured, and thereby unaffected by ambient conditions. The apparatus also allows the practitioner of this invention to readily and accurately measure moisture content.

Abstract: A soil penetrometer and method of using this apparatus are disclosed. The method relates to the application of a constant force to a soil penetrometer, the penetrometer capable of detecting soil moisture content by time domain reflectrometry. The use of the constant force eliminates the variable nature of this parameter conventionally encountered in the art, and therefore reduces the complexity of soil parameter calculation.

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: Methods are provided for determining a solids to liquids ratio in a flowing petroleum stream having an immiscible solids, oil and water flow. Microwave energy in the 10-12 Gigahertz bond is directed through the petroleum stream and attenuated transmitted and reflected microwave energy are detected. The detected microwave energy is compared to an empirically derived map of attenuated amplitude vs. phase for a set of reference petroleum streams having known solid, oil and water contents to derive a solids to liquids ratio for the unknown stream.

Abstract: The displacement sensor of this invention comprises a tube combined with a sonic transmitter and receiver. The tube acts as a waveguide for the sonic waves and a processor determines whether the tube has changed in length or has been constricted which, in either case, changes the pattern of sonic waves traveling from the transmitter to the receiver. In some applications, the transmitter and receiver are at different ends of the tube. In these cases, the attenuation in sound energy reaching the receiver, caused by the tube being squeezed at at least one point, is measured and the amount of cross action area reduction is determined. In other applications, the transmitter and receiver are at the same end of the tube and, in some of these cases, the transmitter and receiver are the same transducer.

Abstract: A sensor for use with time domain reflectometry systems to allow measurement of relative proportions of intermixed constituents having differing electrical permittivities contained in a fluid mixture. The sensor comprises a central primary electrode and a pair of adjacent outer secondary outer electrodes. The fluid mixture is located between the electrodes during sensing. A dielectric layer covers exposed sensing surfaces of the electrodes to electrically isolate the electrodes from the fluid mixture and to prevent dissipation of a time domain reflectometry signal propagated through the sensor.

Abstract: A device for gauging the level of a fluid in a container is described. It comprises a transmitter for transmitting a polarizable microwave signal through a first waveguide section, a receiver for receiving a reflected microwave signal, an electronic unit for determining the reflex position of the reflected microwave signal and an antenna means with a second waveguide section. The device is primarily characterized in that the transmitter and receiver, respectively, transmits and receives a waveguide mode each, mutually orthogonal, and by an easily replaceable third waveguide section (6, 16, 17) inserted between the first (2) and second (5) waveguide sections, provided with means (12, 14, 15, 22) for polarization and/or damping for optimal adaptation of the device to various containers and antennae.

Abstract: Apparatus for measuring a characteristic of a body of material having first and second substantially parallel coaxial lines with distal extremities in relatively close proximity to each other and adpapted to be disposed in close proximity to the body of material. A transmitter is coupled to the first coaxial line for introducing electrical energy in the high frequency to a microwave range into the first coaxial line to cause an electromagnetic field to be established at the distal extremity of the first coaxial line and to extend into the body of material. A receiver is coupled to the second coaxial line for detecting any of the electromagnetic field coupled into it from the first coaxial line. A measurement device is coupled to the receiver means for ascertaining when any change occurs in the coupling of the electromagnetic field from the first coaxial line to the second coaxial line to determine said characteristic of the body of material.

Abstract: A surface condition sensing system includes a frequency controlled source of electromagnetic power adapted to produce a band of selected frequencies which are directed to a surface under examination. A monitoring circuit compares transmitted and reflected electromagnetic power as a function of frequency from the surface, and generates a plurality of absorption signals representing the difference between the amplitude of the transmitted signal with the corresponding amplitude of the reflected signal. An evaluator circuit generates a surface condition signal representing the results of a comparison between the plurality of absorption signals with known surface models. A control circuit generates a status signal representative of the surface condition. The system can be configured as a road condition sensor or as an aircraft ice detection sensor.

Abstract: In an apparatus for determining the material moisture of a medium by measuring the dielectric coefficient of the medium around a measuring probe, wherein the apparatus includes a signal generator providing to one end of the probe a pulse signal, the echo of which, when returning from the other end of the probe, is received by a receiver, and a timing device determining the time elapsed between the introduction of the pulse signal and the return of the echo, the probe consists of a body structure which has electrical signal conductors disposed on its surface.

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: The means and method of the present invention includes a source of microwave energy and associated elements which provide microwave energy to a petroleum stream. Other circuitry include elements which receive microwave energy from the petroleum stream. Electronic apparatus provides at least one outputs utilizing the provided microwave energy, the received microwave energy and known values for 100 percent oil, 100 percent gas and 100 percent water, corresponding to a ratio of gas to liquid. From the readings of attenuation and phase shift, an estimate of the proportions in the mix is extracted by interpolation.

Abstract: A method and apparatus for measuring a level of a material in a tank includes providing a stepped frequency microwave signal to an antenna of a transmitter and receiving in the antenna a received signal from a surface of the material at the level to be measured. A measuring signal containing ranging and calibrating signals is processed in even and odd sample sets input to contiguous narrowband filters formed digitally in a processor using DFT and other algorithms to form true in-phase and quadrature outputs. These outputs are combined and further processed using an interpolation algorithm to isolate ranging and calibration frequency components and to accurately measure the distances represented by such components. The calibration distance associated with the calibration frequency component is compared to a known delay line length and any determined error is used to correct the ranging distance associated with the ranging frequency component.

Abstract: An apparatus and method for measuring the water level at the bottom of a storage tank, the water level being the product-water interface between product and water within the storage tank. The apparatus includes a sensor assembly which is located at the tank bottom. The assembly has a plurality of measurement sensors arranged in a housing having slots for product and water to enter and leave the housing. Each measurement sensor is an open-circuited co-axial transmission line with a probe at its open end which functions as a monopole antenna. In preferred embodiments, the transmission lines are quarter wavelength open-circuited coaxial transmission lines. Each probe is located at a different distance from the tank bottom to cover a measurement range. The transmission lines are excited with signals which are reflected by the probes.

Abstract: A process and a device for determining the moisture content of the material of a test object using microwaves. The properties of a resonator such as resonance frequency, resonance half-width value and amplitude of the resonance can be measured using a digitally tunable quartz-stable PLL-controlled microwave generator. By special processing of the variations in the results due to detuning of the resonator when it is being filled with a product, the moisture content of the material in the product can be measured exactly, independently of the density of the material and largely independently of the type of material and of changes in additives. The same measurement equipment can be used, without any rearrangement of the hardware, both in the ppm range and up to moisture contents greater than 80%. In addition, there are no special requirements concerning the shape of the sample.

Abstract: Time Domain Reflectometry ("TDR") methods and apparatus for measuring propagation velocities of RF pulses to determine material liquid contents, moisture profiles, material levels and dielectric constants including: i) TDR probes and/or probe adaptors, including series averaging probes and multi-segment probes, all employing remotely operable, normally open, variable impedance devices such as diodes; ii) bias insertion and switching networks for rendering selected normally open variable impedance devices conductive one at a time to establish precise unambiguous timing markers T.sub.1 . . . T.sub.

Abstract: The means and method of the present invention includes a source of microwave energy and associated elements which provide microwave energy to a petroleum stream. Other circuitry include elements which receive microwave energy from the petroleum stream. Electronic apparatus provides at least one outputs utilizing the provided microwave energy, the received microwave energy and known values for 100 percent oil, percent surfactant and 100 percent water, corresponding to a ratio of surfactant to oil/water mixture.

Abstract: A device for determining the material parameters, in particular the water content, of a substance in a dielectric medium conducted through a pipeline, the device including a waveguide of a microwave system at least partially enclosing the pipeline. Transmission or reflection of microwave radiation in the waveguide is evaluated continuously or in cycles. Continuous measurement of such media, in particular liquid media, can be effected and in particular can be made automatically without requiring steps for sample taking and performance of the measuring process per se.

Abstract: The invention relates to a measuring apparatus for measuring the condition of a felt in a paper machine, comprising a measuring head (1) connected to a vacuum source. Air is sucked into the measuring head through the felt, and the air and the water carried with the air are removed through separate conduits. The measuring head comprises a microwave head for measuring the water content of the felt, and a temperature detector for measuring the temperature of the sucked air concurrently with the vacuum measurement.

Abstract: In the method of the invention, a microwave signal is passed through a material whose moisture content is to be measured, the change in the velocity of the signal which has travelled through the material is measured and the moisture content is determined on the basis of the measured change and a known interdependence between the changes in the microwave signal velocity and the moisture content of the material. The apparatus comprises a transmitting device (1) which transmits a microwave signal through the material to be measured, and a detecting device (2) and a counting device (3) which measure the change of velocity of the signal transmitted through the material and determine the moisture content of the material on the basis of a known interdependence of the change of velocity of the microwave signal in question and change of moisture content of the material.

Abstract: Apparatus for measuring a characteristic of a body of material having first and second substantially parallel coaxial lines with distal extremities in relatively close proximity to each other and adapted to be disposed in close proximity to the body of material. A transmitter is coupled to the first coaxial line for introducing electrical energy in the high frequency to a microwave range into the first coaxial line to cause an electromagnetic field to be established at the distal extremity of the first coaxial line and to extend into the body of material. A receiver is coupled to the second coaxial line for detecting any of the electromagnetic field coupled into it from the first coaxial line. A measurement device is coupled to the receiver means for ascertaining when any change occurs in the coupling of the electromagnetic field from the first coaxial line to the second coaxial line to determine said characteristic of the body of material.

Abstract: A distance measuring device for measuring the fill level in industrial tanks, which includes electronic transmitting- and receiving elements for short wave electromagnetic waves, such as microwaves, and a cylindrical waveguide which extends through a separating wall and inside of which is a waveguide window separating the two spaces and made of a material, such as quartz glass, which is transmissive with respect to electromagnetic waves. The waveguide and the waveguide window (3) have conically-shaped sections (5) to provide axial support. To protect the waveguide window against destruction due to thermal expansions and pressure fluctuations, the conical section (5) of the waveguide window (3) is in a correspondingly formed conical socket (8). The socket is mounted with play in a cylindrical bore (9) of the waveguide window (3) and is supported by a shoulder (10) of the waveguide in the axial direction.

Abstract: A device and method for measuring the moisture content of a sample using microwaves is provided. The device includes a power supply for outputting an electrical current, a microwave oscillator electrically connected to the power supply for outputting a microwave signal, and a waveguide placed between the microwave oscillator and the sample. The waveguide has a predetermined length and is constructed from copper. A microwave detector outputs a voltage signal which is related to the intensity of the microwave energy reflected by moisture in the sample. A voltmeter displays a reading of the voltage signal output by the microwave detector. The length of the waveguide is selected to maximize the voltage reading of the voltmeter for a given sample. An enclosure houses the power supply, the microwave oscillator, the waveguide and the microwave detector, and is provided with an opening at which the waveguide is mounted. A sheet of microwave transmissive material covers the opening.

Abstract: A water level measurement system for use with a pressurized power plant boiler comprises a tubular pressure vessel for attachment to one end of the boiler such that the water level in the pressure vessel is the same as in the boiler. The pressure vessel has a central rod-like conductor which together with the vessel forms a coaxial RF waveguide. A pair of spaced reference discontinuities are provided in the conductor above the maximum level of the water, so that an RF pulse injected into the waveguide is reflected successively by both discontinuities and the surface of the water. The level of the water can then be determined independently of changes in the dielectric constant of the vapor above it, from the ratio between the time intervals between the first and second reflected pulses and between the first and third reflected pulses. The conductor is mounted at the top of the pressure vessel by way of a pressure seal and a ceramic insulator.

Abstract: A method and apparatus for determining the permittivity of a sample is disclosed. The method includes applying an AC electrical signal in the microwave frequency range via a coaxial probe having an end position near the sample and measuring the reflection coefficient of the sample. The complex permittivity of the sample is determined from an admittance parameter of the sample/probe combination and a system constant. The system constant is determined by measuring the reflection coefficients of four standards having known complex permittivity. The admittance parameter of the sample/probe combination is determined from the admittance parameters of two standards/probe combinations and the measured reflection coefficients of the sample and the four standards. The admittance parameters of the two standard/probe combinations are determined from the known complex permittivities of the two standards and the system constant.

Abstract: Method and apparatus for in vivo or in vitro sensing of complex dielectric properties of lossy dielectric materials, particularly biological tissue. Configured as a needle-like dielectric sensor, a coaxial cable (1) having a circumferential gap (12) in the shield (2) is wrapped with an electrically thin dielectric substrate (18). The cable center conductor (6) extends immediately past gap (12) and is shorted to cable shield (2). A thin conductive dipole resonator (16) is positioned on substrate (18) and over feed gap (12) to achieve inductive coupling between the cable center conductor (6) and the dipole resonator (16) through gap (12). Superstrate (22), which could be a dielectric catheter, covers the entire sensor assembly (10). By measurement of the resonator resonant frequency and the input impedance matching factor at the resonant frequency, the real and imaginary dielectric components (.epsilon.', .epsilon.") of the test material into which the sensor is inserted are determined.

Abstract: Probes for the measurement of moisture content, solids content, and electrical conductivity of porous or fibrous materials, slurries, liquids, and the like using Time Domain Reflectometry comprising a conductive wire or rod extending outwardly from the embedded at one end in, a conductive base and insulated from the base by a region of dielectric material. The wire and base being dimensioned and spaced to emulate a coaxial transmission line with the wire or rod being the center conductor of the transmission line and the conductive base forming the coaxial shield.

Abstract: The conductance meter includes source means which irradiates a fluid with microwave energy. A receiver receives microwave energy that has passed through the fluid and provides the received microwave energy as test microwave energy. Electronic apparatus determines the conductance of the fluid in accordance with the amplitude of the test microwave energy and the phase difference between the microwave energy from the source and the test microwave energy from the receiver where only 1 microwave frequency is used.

Abstract: A system for determining the average water film thickness on surfaces, and in particular roadways, with the reflection of microwaves on the surface of the film of water being measured. To be able to easily measure water film thicknesses of several millimeters without contact and with great accuracy, the system includes at least two partial systems which each comprise a signal source and a receiver. The individual partial systems operate at different frequencies which are selected such that the maximum accuracy measuring regions associated with the respective frequencies are contiguous and cover the predetermined water film thickness range to be determined. The partial systems are connected with a sampling and control device which activates at least that partial system which exhibits maximum measuring accuracy for the respective water film thickness being measured and utilizes only the output signal from the receiver of that partial system for the measurement.

Abstract: Radio frequency bridge techniques are used to parameterize the complex dielectric properties of solids, liquids, gasses and mixtures thereof. This parameterization is performed in an electrically isolated, physically open structure which allows continuous or batch monitoring of the materials and their mixtures. A method and apparatus are provided for measuring the composition of mutlicomponent process streams flowing in pipes or ducts. The method uses the pipe in which the mixture flows as a waveguide in which propagating radio frequency electromagnetic energy is induced through dielectric loaded apertures. The dielectric measurement is performed in an electrically isolated, flow through test section which induces constructive or destructive interference patterns at characteristics frequencies. The characteristic frequency determines the dielectric constant of the mixture. The dielectric properties are used in turn to determine mixture composition.

Abstract: A hygroscopic commodity, such as a continuous stream of shredded tobacco, is transported past one or more sources of electrical energy and past one or more monitoring devices. One of the sources can expose the stream to the electric field of a capacitor in a high frequency oscillator circuit, and the other source can expose the stream to infrared waves or microwaves. The moisture in the stream influences the phase and/or the damping of oscillations of the electrical energy, and the monitoring device of devices ascertain the changes of such characteristics of the electrical energy and transmit corresponding signals to a processing circuit which processes the signals into moisture signals.

Abstract: Method and apparatus for monitoring the volumetric ratio of two constituents of a fluid mixture, e.g. crude oil and water, flowing through a conduit are described. A non-contacting, bidirectional, microwave transmitting/receiving antenna, coupled with a cavity having a conduit through which the fluid mixture passes, generates a signal indicative of the changing dielectric constant of the fluid mixture. By locating the conduit proximate the aperture of the antenna, and by dimensioning the conduit's depth approximately one-fourth the shorter of the two predetermined wavelengths of microwave energy in the two fluid constituents, a substantially linear response of the fluid mixture to the microwave energy incident thereon is produced. The linear response is indicative of the percentage of oil in the fluid mixture flowing through the conduit.