Abstract: A level transmitter for use in a process application measures the height of a product level in a container, e.g., in a tank. The level transmitter includes an electromagnetic wave antenna directed into the tank. An electromagnetic wave source sends an electromagnetic wave signal through the electromagnetic wave antenna. An electromagnetic wave receiver receives the reflected electromagnetic wave signal. Measurement circuitry coupled to the source and receiver initiates transmitting of the electromagnetic wave signal and determines product level height based upon the received, reflected signal. Output circuitry transmits information related to product height. The device is suitable for use with containers having very small orifices for antenna insertion.

Abstract: A method and apparatus for monitoring one or more parameters of a variable physical structure, such as liquid level, is disclosed. The method and apparatus includes an electrodynamic element placed in proximity to a monitored structure and exciting within said element an alternating electromagnetic field. The electromagnetic field should be at a frequency at which the electromagnetic field penetrates into the monitored structure and then variations of the electromagnetic field parameters are measured for the element caused by a variation in the structure. The exciting of the electrodynamic element is by an electromagnetic field in the form of at least one slowed electromagnetic wave having suitable energy distribution of the electric and magnetic fields for the measuring of the electromagnetic field parameters.

Abstract: A method and tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is described for the detection of external sidewall cracks and other anomalies in boiler tubes and other enclosures. The invention utilizes the concept of radar backscatter rather than eddy-currents or ultrasound, which are sometimes used in prior art crack-detection methods. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to −40 dB in thin-walled boiler tubes.

Abstract: A system and method for detecting anomalies such as corrosion or other defects in or on conductive containers such as pipes, pipelines, separator containers, and storage tanks. An electromagnetic pulse is introduced onto the surface of the container itself, if not insulated or shielded, or the surface of the very outer layer of the shield or insulation, if the container is insulated and shielded, of the conductive container at a first test location such that a plurality of electromagnetic signals propagate from the first test location to a second test location. The electromagnetic signals are detected at the second location and analyzed for differences in electromagnetic characteristics that indicate the presence or absence of electromagnetic anomalies related to corrosion and/or defects. Each electromagnetic signal propagates along a unique path, and the corrosion is likely to lie on some but not all of these paths.

Abstract: The invention relates to a device (1) for determining the filling level in a container (4). Moreover, the invention also relates to a method for fastening an input coupling unit (9) on the antenna (7), the antenna (7) being used in the device (1) according to the invention. It is the object of the invention to provide overvoltage protection for an antenna (7), and a method for producing such an antenna (7). The object is achieved by virtue of the fact that the antenna (7) comprises at least two dielectric layers (12, 13). The first dielectric layer (12) has at least one cutout (15) for holding the input coupling unit (9). The second dielectric layer (13) bears an antenna structure (16) on the side facing the first dielectric layer (12) and has a conductive coating (17) with openings (18) on the side averted from the first dielectric layer (12). Contacts (19) are provided in the second dielectric layer (13) and the conductive layer (17) which connect the input coupling unit (9) to the conductive coating (17).

Abstract: A position detection apparatus which can control an apparatus to be controlled, such as a motor or the like, more precisely, is disclosed. When a predetermined time has passed since reception of a request signal for requesting output of the position data was detected, the position detector measures the output of a sensor for detecting the position of an object to be measured, and calculates the position data representing the position of the object at a point of time when the measurement was performed, based on the measured output.

Abstract: The method for measuring the thickness of a material which transmits a detectable amount of microwave radiation includes irradiating the material with coherent microwave radiation tuned over a frequency range. Reflected microwave radiation is detected, the reflected radiation having maxima and minima over the frequency range as a result of coherent interference of microwaves reflected from reflecting surfaces of the material. The thickness of the material is determined from the period of the maxima and minima along with knowledge of the index of refraction of the material.

Abstract: An arrangement for measuring the liquid level in a tank. The arrangement has a microwave transmitting/receiving device and a waveguide that extends into the tank for guiding a coupled-in microwave. The waveguide has clear and constant wave propagation characteristics for a wave with the operating frequency.

Abstract: An improved time domain reflectometer (TDR) includes a capacitor coupled in series between a transmission medium under test and the TDR receiver input. A switch, operating under microprocessor control, selectively couples and uncouples the capacitor to a voltage reference, such as ground. During the generation of interrogating pulses from the TDR and the acquisition of data from the transmission medium under test, the capacitor is uncoupled from the voltage reference and acts as a DC blocking capacitor. During periods of non-TDR activity, the capacitor is coupled to voltage reference and acts as a load for low frequency interference appearing on the transmission medium. The capacitor-switch operation blocks low frequency interference signals from the receiver input of the TDR.

Abstract: An angle detecting apparatus having a simple structure can reliably detect the rotational angle of an object. The apparatus has a rotary shaft, a first conductor arranged in an open loop around the rotary shaft, a second conductor positioned very close to the first conductor and arranged so as to rotate relative to the first conductor, and an angle sensing circuit. The angle sensing circuit generates an original pulse P1, which is input to one end of the first conductor and propagates through it. A portion of the pulse is reflected by the second conductor, and received by the angle sensor as a first reflected pulse P2. The angle sensing circuit determines the angular position of the second conductor based on the time required to receive the first reflected pulse P2. The angle sensor also receives a second reflected pulse P3 which was reflected by the other end of the first conductor.

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: The thickness of the layers of rubber covering the steel belts within a tire can be measured by transmitting a microwave signal toward the outer surface of the tire and measuring the phase shift of the signal reflected by the tire. In the preferred embodiment, a waveguide is used to direct the microwave signal toward the tire. A standing wave is created within the waveguide by interference between the transmitted microwave signal and the microwave signal reflected from the tire. A series of crystal detectors mounted along the length of the waveguide measure the standing wave. A processor calculates the phase of the reflection coefficient, and determines the thickness of the rubber layer as a predetermined function of the phase. By proper selection of the microwave frequency and the spacing between the waveguide and the tire, the rubber layer thickness can be uniquely determined as a function of phase for any range of rubber thicknesses likely to be encountered in a tire.

Abstract: A waveguide for microwave radar level gages that includes a process sealed barrier in the waveguide that is impedance matched with bore transition sections of the waveguide at opposite ends thereof. The impedance matching results in positioning of the tapered end of the barrier offset from the ends of the bore transition sections.

Abstract: An electromagnetic, reflective type, active proximity sensor includes a transmitter, the transmitter including a voltage controlled oscillator circuit, a transmitter circular waveguide and a transmitter polarization circuit. The voltage controlled oscillator circuit generates an output signal which is modulated such that the frequency of the output signal varies over time between a range of frequencies. The frequency varying, output signal is provided to the transmitter circular waveguide and propagated to the transmitter polarization circuit where it is circularly polarized in a first circular direction. The circularly polarized, frequency varying, output signal is radiated by the transmitter to the target, where it strikes the target and reflects back toward the sensor to form return signals. The return signals, upon being reflected, rotate in a second circular direction opposite to the first circular direction.

Abstract: A proximity detector including a sensor unit that produces an analog signal and a processor circuit digitizing this signal. The processor circuit includes logic that determines a switching value from an initial value and an extreme value obtained during a learning mode.

Abstract: A millimeter wave sensor is provided for non-destructive inspection of thin sheet dielectric materials. The millimeter wave sensor includes a Gunn diode oscillator (GDO) source generating a mill meter wave electromagnetic energy signal having a single frequency. A heater is coupled to the GDO source for stabilizing the single frequency. A small size antenna is coupled to the GDO source for transmitting the millimeter wave electromagnetic energy signal to a sample material and for receiving a reflected millimeter wave electromagnetic energy signal from the sample material. Ferrite circulator isolators coupled between the GDO source and the antenna separate the millimeter wave electromagnetic energy signal into transmitted and received electromagnetic energy signal components and a detector detects change in both amplitude and phase of the transmitted and received electromagnetic energy signal components.

Abstract: A process sealed waveguide is formed in a flange mounted on a tank, and is used for transmitting microwave energy from a source of microwave energy to an aperture of an antenna on the interior of the tank. The process sealed waveguide includes a mechanical barrier to prevent escape of fluid under pressure or liquid from the interior of the tank, and also serves to reduce impedance mismatch between the air, vapor, or liquid filled waveguide or antenna apertures. The flange is mated to the microwave source through an electronic housing to flange adapter that interfaces with the flange in a manner to provide a vent in case the mechanical barrier fails so pressure is released, and to provide flame quenching if flames are present. The adapter includes a second waveguide having a process sealed mechanical barrier mounted coaxially with the mechanical barrier in the waveguide in the flange.

Abstract: Microwave radiation emitted from a single antenna is focused on a targeted material from which reflected radiation is received by the same antenna to provide signal measurement data from which detected material defects are evaluated by determination of void location and size. Antenna position and orientation is adjusted to obtain the signal measurement data from of the microwave radiation reflection along at least two target incidence paths from the same target location, one of which is normal to said targeted surface of the material and the other oblique thereto at a scattering angle at which the signal radiation intensity is minimized.

Abstract: A level sensor for use in a process application measures height of a product in a tank. The level meter includes a microwave feedhorn directed into the tank, an electronics housing spaced apart from the feedhorn and a microwave waveguide extending therebetween. A microwave transducer in the housing couples to the waveguide and sends and receives microwave signals. A microprocessor in the housing identifies echoes from the microwave signals which are generated and sensed by the microwave transducer. The microprocessor determines height of the product based upon a microwave echo from the product and a microwave echo from the feedhorn. The microprocessor compensates for the effect of propagation delay through the waveguide on height measurements with the feedhorn echo and provides an output related to height of the product in the tank.

Abstract: The ability to be able to identify, distinguish and verify a lock onto harmonic frequency signals in the oil of a hydraulic cylinder using a ratio between consecutively detected harmonics. The identification is useful in providing early and reliable harmonic resonance "lock on" and the ability to "lock on" to a particular order harmonic resonance.

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: An apparatus and method is disclosed for the location of faults occurring within transmission systems. The disclosed apparatus and method allows a user to adjust the center frequency of a pulse output by a standard narrow bandwidth time domain reflectometer, without altering the bandwidth of the output pulse. As a result, the detection of faults occurring at a wide range of frequencies is enabled--while the cost associated with widening the bandwidth of the transmitted pulse is not incurred. Moreover, due to the narrower bandwidth, efficient fault detection is achieved as well for high frequency systems as for low frequency systems.

Abstract: A method and apparatus for determining fatigue/surface crack features on metal surfaces is disclosed wherein the cracks may be empty, filled, or covered with a dielectric (e.g., paint). The present invention includes a microwave waveguide having an aperture for scanning over a surface and thereby characterizing changes in a standing wave within the waveguide when a crack is scanned. In particular, crack related data resulting from standing wave perturbations can be analyzed for determining crack geometric features such as crack width, crack depth, crack length and crack tips. These features are determinable with high precision in comparison to the size of the aperture. When locating and/or sizing the geometric features of a crack, voltage changes induced by higher order modes generated by various orientations of the crack in relation to the aperture are utilized for generating the crack related data.

Abstract: The composition of an electrically conductive mixture, preferably a mixture of gasoline and alcohol, is measured using a single measurement cell having a first electrode and a second electrode with a measurement space therebetween for receiving a specimen of the mixture. With a specimen of the mixture in the measurement space, the first electrode is alternatively connected to a reference discharge voltage, preferably ground, and to a feedback control voltage. A first operational state encompasses the period when the first electrode is connected to the reference discharge voltage and a second operational state encompasses the period when the first electrode is connected to the feedback control voltage. A first operational state peak voltage is measured during the first operational state, and a peak second operational state voltage is measured during the second operational state.

Abstract: An apparatus for checking the authenticity of a security document (28). The security document (28) comprises a base material and in its volume particles having some electromagnetic properties which are substantially different from the corresponding electromagnetic properties of the base material. The apparatus comprises at least one emitter (18) for emitting near infrared or visible waves to the document (28), at least one detector (20) for detecting any of the emitted near infrared or visible waves reflected from the document (28) and means (30) for processing the detected near infrared or visible waves in order to differentiate the security document (28) from a document comprising electromagnetic particles or parts on its surface.

Abstract: A level transmitter for use in a process application measures height of a product in a tank. The level transmitter includes a microwave antenna directed into the tank. A low power microwave source sends a microwave signal through the microwave antenna. A low power microwave receiver receives a reflected microwave signal. Measurement circuitry coupled to the source and receiver initiates transmitting of the microwave signal and determines product height based upon the received, reflected signal. Output circuitry coupled to a two-wire process control loop transmits information related to product height over the loop. Power supply circuitry in the level transmitter coupled to the two-wire process control loop receives power from the loop which powers the level transmitter including the microwave source and the microwave receiver.

Abstract: A method and apparatus for sensing proximity of an object using near-field effects or magnetic effects. The sensor chips are designed to accommodate numerous sensing elements. In the electromagnetic sensor, radio frequency energy is fed to an antenna. The antenna radiates this radio frequency energy to charge the surface of an object. When the position of the object changes, the impedance of the antenna due to near-field effects changes. This impedance change is detected to provide an indication of the object's movement. In the magnetic sensor, the sensing element is placed at a right angle to the sensor electronics to provide a smaller surface area across the diameter of the sensor. The magnet that charges the object to be detected is manufactured as a part of the sensor encapsulant. The sensing device may be packaged to be inserted into a wall to provide a sensor having a leak-free seal.

Abstract: A dielectric-loaded, microwave sensor which can detect dielectric coatings, e.g., air, water and ice, on a road surface. The sensor includes an antenna having an aperture and also includes a dielectric member with a lower surface and an upper surface. The dielectric member is arranged with its lower surface across the antenna aperture and the sensor is embedded in a road with the dielectric member's upper surface coplanar with the road's surface. An antenna beam, which is incident upon the dielectric member, generates a return microwave signal which is the composite of microwave reflections from the dielectric member's inner and outer surfaces. Air, water and ice can be uniquely identified by the absence or presence of an amplitude minimum at predetermined frequencies of the return microwave signal. The thickness of an ice coating is determined by observation of the frequency of the amplitude minimum.

Abstract: A method and apparatus (10) for sensing a surface level (24) of fluid (12) in a tank (14) having an electrically conducting pickup tube (20) extending through a wall (16) of the tank (14) and into the fluid (12) includes a time domain reflectometry circuit (40) connected to the tube (20) for generating an incident pulse (68) that travels down the tube (20) and a portion of which is reflected at the surface (24) as a reflected pulse (70,72) which travels back along the tube (20) and is sensed by the circuit (40). The circuit (40) includes a microprocessor (92) which utilizes the elapsed time between the generation of the incident pulse (68) and the receipt of the reflected pulse to determine the position of the surface (24) relative to a reference point and the amount of the fluid (12) in the tank (14) and indicate the amount of fluid at a display (106). The tube (20) forms a transmission line with one of a plate (48), an outer tube (110) and a return tube (130).

Abstract: An apparatus for sensing the proximity of a moving target is provided which includes a sensor for sensing a range of distances between a reference point and a moving target. The sensor preferably has a detector for detecting a distance signal representative of a range of distances between a reference point and a moving target and a maximum and minimum generator responsive to the detector for generating a maximum distance range DC voltage signal representative of a maximum distance range value between a reference point and a moving target and for generating a minimum distance range DC voltage signal representative of a minimum distance range value between a reference point and a moving target.

Abstract: A low power, low cost, millimeter wave (MMW) proximity sensor that provides over a 6:1 increase in minimum detection range (55 mm minimum) compared to standard 18 mm inductive proximity sensors preferably includes a low cost MMW Gunn oscillator, MMW detector and analog processing/driver circuitry. The sensor is preferably designed for 3-wire operation and will fit in a standard 18 mm tube.

Abstract: A distance measuring system for measuring a distance between two objects has a transmitter assembly mounted on one of the two objects, for transmitting a plurality of electromagnetic waves having respective wavelengths different from each other at respective levels toward the other of the two objects, a receiver assembly mounted on the other object, for receiving the electromagnetic waves transmitted from the transmitting means, and a distance detector for detecting a ratio of levels at which at least one set of electromagnetic waves of the electromagnetic waves is received by the receiving means, as corresponding to a distance between the two objects, and determining the distance between the two objects from the ratio.

Abstract: The present invention relates to a method and related apparatus for the nondestructive determination of n layers of coating of a target having n layers of dielectric coating applied to an electrically conductive base material, comprising; a generator of electromagnetic waves in the microwave frequency range, including a microwave oscillator, a waveguide attached to the oscillator output and having an output aperture, a voltage detecting diode disposed within the waveguide, a flat layer of material adapted to be placed in a position abutting the target and disposed over the aperture of the waveguide and having a thickness t which, together with the waveguide, will provide a fixed distance between the diode and the target, and a display responsive to the output of the detecting diode for indicating the layer characteristics of the dielectric coating on the electrically conductive base material.

Abstract: A time domain reflectometer includes a clock signal source that synchronizes a Start pulse source which, in turn, generates a succession of Start pulses. Each succeeding Start pulse, after an initial Start pulse, is delayed in time from a preceding Start pulse by a test pulse interval plus a delay time. A test pulse circuit responds to each Start pulse by applying a test pulse to the LUT. A reflection signal sampling circuit samples N reflection signals in synchronism with the clock signal source, whereby successive ones of the N reflection signals are sampled at different delay times as a result of the delay time added to each succeeding Start pulse. A memory circuit assembles sampled reflection signal values from the N reflection signals in a manner that the reflection signal values are interleaved in time order as though all sampled reflection signal values were obtained from a single reflection signal.

Abstract: An apparatus (102) and method for detecting the position of a piston and piston rod (104,106) within a housing (108) of a hydraulic cylinder (110). The piston (104), piston rod (106), and housing (108) form first and second coaxial resonant cavities (114,116). A first location of the piston and piston rod (104,106) is determined as a function of the resonant frequency of one of the coaxial cavities (114,116). A second location of the piston and piston rod (104,106) is determined as function of the resonant frequency of the other cavity if the first location is invalid.

Abstract: A method and apparatus for detecting fluid level in a tank in the vicinity of a transmission line (1), the fluid level being such as to cause reflection of a signal transmitted along the transmission line. The method includes the steps of:a) transmitting a signal along the transmission line;b) monitoring the transmission line for any reflections of the signal;c) generating an analysis window of time (t.sub.1, t.sub.2, t.sub.3) if the magnitude of a given characteristic of the reflected signal is greater than a predetermined threshold value; andd) analyzing the reflected signal received during the period of an analysis window to provide the required information on the fluid level.

Abstract: A method and apparatus for sensing proximity of an object using near-field effects. Modulated radio frequency energy is fed to an antenna. The antenna radiates this modulated radio frequency energy to charge the surface of an object. When the position of the object changes, the impedance of the antenna due to near-field effects changes. This impedance change is detected to provide an indication of the object's movement. The sensing device may be packaged to be inserted into a wall to provide a sensor having a leak-free seal.

Abstract: A system for measuring the gap between two surfaces is disclosed. The sensing apparatus comprises an actuator, an active sensor and a display. The actuator actuates operation of the sensing apparatus. The active sensor includes a transmitter for transmitting a wave signal beam reflectable off one of the surfaces and a receiver for receiving the reflected wave signal beam by the sensing apparatus. A signal processor is in electrical communication with the actuator, the transmitter and the receiver, for processing the reflected wave signal beam to determine the gap between the two surfaces. The display is in electrical communication with the signal processor for displaying the amount of gap between the two surfaces.

Abstract: Apparatus and method for detecting, determining, and imaging surface resistance corrosion, thin film growth, and oxide formation on the surface of conductors or other electrical surface modification. The invention comprises a modified confocal resonator structure with the sample remote from the radiating mirror. Surface resistance is determined by analyzing and imaging reflected microwaves; imaging reveals anomalies due to surface impurities, non-stoichiometry, and the like, in the surface of the superconductor, conductor, dielectric, or semiconductor.

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 method and apparatus for the measuring of a delay in a delay circuit by making a continuous frequency measurement is proposed. The phase-locking of a variable frequency signal applied to the delay circuit allows the user to significantly improve the precision and accuracy of the time delay measurement. A scheme to extract the number of cycles stored in the delay circuit is also disclosed.

Abstract: A portable microwave instrument for evaluating characteristics of a structural member includes a source of microwave energy, a transmitter coupled to the source of microwave energy for transmitting a microwave signal at the structural member, and a receiver positioned on the same side of the structural member as the transmitter and being disposed to receive a microwave signal reflected by the structural member. A phase angle difference is determined between the transmitted microwave signal and the received microwave signal using a signal splitter and a balanced mixer. The difference in phase angle varies in accordance with differences in size, shape and locations of constituent materials within the structural member.

Abstract: A parallel plate transmission line (20) is formed by conformal application of one or more dielectric and conductive layers to the surface under test (70). A signal generator (42) is employed to transmit variable frequency signals (60) along the transmission line (20). Discontinuities in the transmission line (20) cause reflections (62) which are received by a receiver (48). A processor (44) coupled to the signal generator (42) and receiver (48) detects and locates the discontinuities.

Abstract: An electrical device for measuring the liquid level in industrial tanks and the like with a microwave transmitter and receiver and a waveguide provided with an aperture and an antenna. The signal reflected from the liquid surface and the transmitted signal are fed to a frequency conversion stage (8), whose low-frequency output signal is sent via an A/D converter (12) to a microprocessor calculating the fill level. To reduce the effect of interference frequencies produced by reflection of microwaves in the optical aperture, etc., a band-pass filter (9,10) with a lower limiting frequency selected to attenuate the low-frequency interference frequencies is placed between the frequency conversion stage (8) and the A/D converter (12). The lower limiting frequency can either be controlled with microprocessor (13) or the band-pass filter (9, 10) has adjustable limiting frequencies.

Abstract: In a microwave imaging system, a three dimensional profile of the dielectric permittivity of a target is obtained. A transmitter transmits microwaves toward a target, and the target scatters the microwaves. The scattered waves are received by an antenna and are converted into suitable data for application to a digital computer. The computer processes the data using either a scattering matrix algorithm or a Fourier transform algorithm. The computer then generates data representative of a three dimensional profile of dielectric permittivity which can be displayed on a suitable display device such as a CRT.

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: 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 method and system for monitoring the level of flowable material contained in a transportable vessel that utilizes microwave gauging technology. The system includes a microwave lens/seal assembly, a microwave transceiver assembly, a controller/processor assembly and a computer. The lens/seal assembly is permanently secured to the vessel. The microwave transceiver assembly is adapted to be releasably attached to the vessel. The controller/processor assembly and the computer may be located at a loading/unloading facility.

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.