Abstract: A measurement device for measuring a thickness of a film layer over a substrate utilizes a microwave source and a resonant cavity having an open side. A microwave signal is introduced at a first end of the resonant cavity with the open side against a surface measurement sample having a film layer over a substrate, and an output signal detector senses the output power of the signal at a far end of the resonant cavity. A processor uses a difference in the resulting resonant frequency of the cavity from that using a substrate without the film layer to determine the thickness of the film layer.

Abstract: An apparatus and method for detecting a defect on a ground layer of microstrip by using scattering parameters is disclosed. The apparatus includes: a providing unit for providing a signal to the microstrip by changing a frequency of the signal in a predetermined range of frequencies; a detecting unit for detecting scattering parameters of an output signal from the microstrip in response to the frequency of the signal; and an analyzing unit for analyzing the interface based on the scattering parameters.

Abstract: An electronics package for use with a proximity probe is disclosed that is capable of being calibrated to work with any proximity probe and cable and that is capable of being programmed in the field. The electronic package establishes and measures a plurality of gaps between the proximity probe and a target. An amplifier is operatively coupled to the proximity probe and produces an output which is digitized, linearized and stored. A linear piecewise approximation technique is used to approximate the voltage at the output of the amplifier for gaps that were not measured.

Abstract: Film thickness measurement systems and methods are provided that utilize a signal generator having a Gunnplexer design and a resonant frequency detector to correlate the shift in resonant frequency experienced by a resonant cavity having one face abutting a test object. The shift is resonant frequency is determinative of a linear or near linear correlation between film thickness and the resonant frequency shift.

Abstract: A device is disclosed, comprising a microwave resonator, for or on a spinner preparation machine with drawing gear (2) for drawing fiber material (FB), in particular a carding, drawing or combing machine, whereby the resonator (30) is embodied for connection to a measuring device (16) for measuring the strip density (mass per unit length) or the strip thickness and/or the dampness of the fiber material (FB), continuously passing through the resonator chamber (31). Said device is characterized in that the resonator (30) is integrated in a functional group (20; 120; 220; 320; 420) of the spinner preparation machine which is typical for the machine. A spinner preparation machine, in particular a carding, drawing or combing machine, is further disclosed which comprises a corresponding device.

Abstract: An ultrasonic distance measure includes: transmitting and receiving ultrasonic transducers with changeable resonant/resonance frequencies; a driving section generating a frequency-modulated drive signal to drive the transducer and transmit an ultrasonic wave; a transmitting control voltage generating section for generating a control voltage to change the resonant/resonance frequency of The transducer and applying it to the transducer in transmitting the ultrasonic wave; a receiving control voltage generating section for generating a control voltage to change the resonant/resonance frequency of the transducer and applying it to the transducer when a controllable amount of time delay has passed since The drive signal was generated; and a receiving section for sensing the intensity of a signal received as the ultrasonic wave at the transducer.

Abstract: A sensing assembly senses liquid levels in a reservoir and creates a sensing signal. The sensing assembly includes a first electrical conductor and a second electrical conductor extending into the reservoir. A first electrode is electrically connected to the first electrical conductor. A second electrode is electrically connected to the second electrode conductor. The sensing assembly also includes a plurality of equidistantly spaced plates that are operatively connected to the second electrode. Each of the plurality of plates combines with the first electrode to create a capacitance such that the sensing signal generating by the sensing assembly determines the level of the liquid in the reservoir. The plates, an inductor and resistors are connected together in series with each of the groupings being connected in parallel to each other along the second electrode length. The sensing signal will generate spikes that, based on amplitude, will identify the amount of a liquid in the reservoir.

Abstract: A high-frequency oscillation proximity sensor with an improved detection sensitivity uses, as a detection coil 11, a two-thread coil formed of substantively two coil conductors joined together at their first ends to form a joint connection end and twisted together, one of the two coil conductors being used as a resonance circuit coil L1 and the other as a copper resistance compensation coil L2, and comprises a drive circuit 12 for supplying a drive current to the joint connection end of the two-thread coil to thereby drive the detection coil to oscillate, a buffer 13 for taking out an oscillating output voltage generated at the joint connection end of the two-thread coil, and a phase shift circuit 15 for turning the phase of the oscillating output voltage taken out by the buffer by a predetermined angle and feeding it back to the copper resistance compensation coil to thereby negate the copper resistance of the two-thread coil.

Abstract: A non-destructive method of detecting and measuring machining induced surface defects on gas turbine engine components is provided. In an exemplary embodiment, the method includes positioning an evanescent microwave microscope probe adjacent a turbine component surface, and scanning the turbine component surface by moving at least one of the evanescent microwave microscope probe and the component surface in an x-y plane while maintaining a predetermined distance between the probe and the component surface constant.

Abstract: The system of the invention for measuring characteristics of thin conductive and non-conductive material, such as bulk material or films, is based on the use of a resonance oscillating circuit that incorporates at least two components selected from the group consisting of an inductive coil and a capacitor, which in combination form a sensor that could be approached close to the surface to be measured. The measurement of the film or material characteristics, such as film resistance (film thickness) or a dielectric constant (film thickness) of a non-conductive material, is based on the principle that the sensor is approached to the measured surface at a distance, at which the inductance and capacitance of the sensor generate in the measured material a virtual coil and an additional capacitance, which strongly depend on the characteristics of the measured material.

Abstract: A method of monitoring a clearance distance between a rotatable member and a stationary member within a rotary machine is provided. The method includes exciting a probe with a first modulation signal when the rotatable member is rotating at less than or equal to a predetermined rate, exciting the probe with a second modulation signal when the rotatable member is rotating at greater than the predetermined rate, measuring the clearance distance between the rotatable member and the stationary member using the probe excited with at least one of the first modulation signal and the second modulation signal.

Abstract: The system of the invention for measuring characteristics of thin conductive and non-conductive material, such as bulk material or films, is based on the use of a resonance oscillating circuit that incorporates at least two components selected from the group consisting of an inductive coil and a capacitor, which in combination form a sensor that could be approached close to the surface to be measured. The measurement of the film or material characteristics, such as film resistance (film thickness) or a dielectric constant (film thickness) of a non-conductive material, is based on the principle that the sensor is approached to the measured surface at a distance, at which the inductance and capacitance of the sensor generate in the measured material a virtual coil and an additional capacitance, which strongly depend on the characteristics of the measured material.

Abstract: The system and method are based on stabilization of the distance between the sensor coil and the surface of the film being measured by constantly measuring the angle of inclination &agr; of a tangent to the curve that represent dependence of the resonance power of the sensor-film system from the distance between the sensor and the film. The aforementioned angle is calculated plotting the resonance curve of a signal, calculating the area between the resonance curve and the abscissa axis, plotting the curve that represent dependence of the aforementioned area from the distance between the sensor coil and the film, measuring the angle &agr; in a preselected point on the last-mentioned curve, and maintaining the distance between the sensor coil and the film constant by keeping angle &agr; constant in a any measurement point. Angle &agr; can be selected within the range of 0 to 90° C.

Abstract: A high-frequency oscillation proximity sensor with an improved detection sensitivity uses, as a detection coil 11, a two-thread coil formed of substantively two coil conductors joined together at their first ends to form a joint connection end and twisted together, one of the two coil conductors being used as a resonance circuit coil L1 and the other as a copper resistance compensation coil L2, and comprises a drive circuit 12 for supplying a drive current to the joint connection end of the two-thread coil to thereby drive the detection coil to oscillate, a buffer 13 for taking out an oscillating output voltage generated at the joint connection end of the two-thread coil, and a phase shift circuit 15 for turning the phase of the oscillating output voltage taken out by the buffer by a predetermined angle and feeding it back to the copper resistance compensation coil to thereby negate the copper resistance of the two-thread coil.

Abstract: Techniques for determining the distance between a measuring apparatus and an object are provided. The measuring apparatus includes a transmitter, a receiver and a filter module having a defined phase frequency characteristic, in which a modulated signal, in particular a light signal, is transmitted in the direction of the object by the transmitter, the signal reflected by the object is received by the receiver and the output signal of the receiver is delivered to the transmitter at least via the filter module, wherein at least the transmitter, the receiver and the filter module form a resonant circuit, the frequency of resonance of the resonant circuit is measured and the distance is determined from the frequency of resonance. The respective frequency of resonance of the resonant circuit is determined for at least two different phase frequency characteristics.

Abstract: A system for detecting overlapped flat objects in a sequence of flat objects have at least one of their edges exposed for viewing as they pass along a feed path. The system includes a sensor for generating a signal in response to detecting a flat object in the feed path and a camera responsive to the signal for capturing a digital image of the exposed edges of the detected flat object in the feed path. A vision system is coupled to the camera for receiving the digital image. The vision system analyzes at least a portion of the image to determine a pixel density variation along a direction perpendicular to the edges and uses the pixel density variation to output an indication of the number of edges in the image.

Abstract: A proximity sensor, in particular a proximity switch is described. A component that pertains to a system variable and is independent from the material of a trigger or target is elected and transformed into a non-periodic signal that depends upon the distance of the trigger. The trigger of a proximity sensor can thus be exchanged randomly without requiring subsequent adjustments. The impedance of an oscillation circuit which pertains to the proximity sensor, the impedance of an oscillation circuit coil, the amplitude of the oscillation circuit signal or a voltage divider ratio between the oscillation circuit and the additional resistance can be used s system variables for instance.

Abstract: A preamplifier portion 2 is arranged between a head portion 1 containing a detecting coil and an amplifier portion 3. wherein a detecting circuit and a controlling circuit and the like are arranged. The preamplifier portion 2 is connected to the head portion 1 via a shielded cable 5 of fixed length, while connected to the amplifier portion 3 via multi core cables 6a and 6b having connectors 7a and 7b. In the preamplifier portion 2, in addition to an oscillating circuit, an EEPROM containing a compensating table for compensating the relation between the oscillation output of the oscillating circuit and a detected distance is arranged. This EEPROM is connected to the controlling circuit at the side of the amplifier portion 3.

Abstract: A quite novel electromagnetic wave source probing device and a method with such a device in which the probing time can be shortened. Magnetic field to time characteristics generated from a subject to be measured are measured in a plurality of positions. Electric field to frequency characteristics generated from the subject to be measured are calculated by use of the plurality of measured magnetic field to time characteristics. Frequency components exceeding a predetermined electric field value are extracted in the calculated electric field to frequency characteristics. Positions where currents having the extracted frequency components exist in the subject to be measured are outputted.

Abstract: The invention pertains to a level measuring by an apparatus has oscillating fork (1) that is excited to oscillate by an oscillator circuit that, for example, is realized in the form of a series circuit consisting of an input amplifier (2), a band filter (3) and an output amplifier (4). An identifying element (6) is assigned to the oscillating fork (1), with the identifying element transmitting the fundamental frequency of the oscillating fork (1) to the oscillator circuit (2, 3, 4) in coded form. In addition, the identifying element (6) transmits the fundamental frequency of the oscillating fork (1) to the control input of a frequency evaluation circuit (5), the input of which is connected to the output of the oscillator circuit (2, 3, 4). Consequently, the parameters of the band filter (3), as well as of the frequency evaluation circuit (5), are optimally adjusted to the fundamental frequency of the oscillating fork (1).

Abstract: In a scanning microwave microscope including a microwave resonator, an exciting unit for exciting the microwave resonator, a first detecting unit for detecting a first detection amount relating to a resonant state of the microwave resonator, a sharp end coupled to a center conductor of the microwave resonator, and a display unit for displaying the first detection amount while a sample is scanned by the sharp end, a distance changing unit causes a differential change in a distance between the sharp end and the sample. A second detecting unit detects a second detection amount relating to a change of the first detection amount. A control unit controls the distance between the sharp end and the sample in accordance with the second detection amount, so that an average value of the distance between the sharp end and the sample is brought close to a definite value.

Abstract: The invention is directed to a system and method for non-invasive pipe inspection. According to one embodiment, the system includes a processor, an analyzer, and a wave launcher. The wave launcher is adapted to transmit an input wideband waveform having a selected input energy into the pipe along a longitudinal axis, and to receive from the pipe a reflected component of the input waveform having a reflected energy. The analyzer is adapted to generate the input waveform, and to receive the reflected component of the input waveform from the wave launcher. The processor is adapted to compare the input waveform with the reflected component of the input waveform to determine characteristics.

Abstract: The subject of the invention is a coating thickness gauge with at least one measuring probe (14) which has at least one sensor (15, 15′) as well as a device for the zero adjustment and/or calibration. The coating thickness device (10) is equipped with means to automatically activate zero adjustment and/or calibration when an interaction especially a contact or a relative movement between a sensor (15, 15′) and a reference plate (11, 11′).

Abstract: The invention relates to a method and a device for measuring the distance between a sensor electrode and a workpiece. The sensor electrode forms, with the workpiece, a measuring capacitor through which an alternating current flows. A voltage present at the sensor electrode is tapped as a measuring voltage. In order to be able to remove the disturbing influence on the impedance of the measuring capacitor of a plasma forming between the sensor electrode and workpiece, the real part and the imaginary part from the measuring voltage are analyzed and used to determine the distance between the sensor electrode and the workpiece.

Abstract: An object recognition method for an intelligent cruise control system of a vehicle with an electronic control unit for performing cruise control and two sensors in communication with the electronic control unit for sensing distance between the vehicle and at least one forward object is provided, which includes: determining a shape of a lane marker; detecting distances from the two sensors to a forward object, and determining a shape of the forward object using the distances; determining whether the shape of the lane marker coincides with the shape of the forward object; and determining that the forward object is a stationary object if it is determined that the shape of the lane marker coincides with the shape of the forward object.

Abstract: A quite novel electromagnetic wave source probing device and a method with such a device in which the probing time can be shortened. Magnetic field to time characteristics generated from a subject to be measured are measured in a plurality of positions. Electric field to frequency characteristics generated from the subject to be measured are calculated by use of the plurality of measured magnetic field to time characteristics. Frequency components exceeding a predetermined electric field value are extracted in the calculated electric field to frequency characteristics. Positions where currents having the extracted frequency components exist in the subject to be measured are outputted.

Abstract: A proximity sensor, in particular a proximity switch is described. A component that pertains to a system variable and is independent from the material of a trigger or target is elected and transformed into a non-periodic signal that depends upon the distance of the trigger. The trigger of a proximity sensor can thus be exchanged randomly without requiring subsequent adjustments. The impedance of an oscillation circuit which pertains to the proximity sensor, the impedance of an oscillation circuit coil, the amplitude of the oscillation circuit signal or a voltage divider ratio between the oscillation circuit and the additional resistance can be used s system variables for instance.

Abstract: Described is a distance-measuring device and a method for determining a distance, which uses a sensor in the form of a cavity resonator to continuously perform a distance determination and allows diverse possible uses.

Abstract: In a scanning microwave microscope including a microwave resonator, an exciting unit for exciting the microwave resonator, a first detecting unit for detecting a first detection amount relating to a resonant state of the microwave resonator, a sharp end coupled to a center conductor of the microwave resonator, and a display unit for displaying the first detection amount while a sample is scanned by the sharp end, a distance changing unit causes a differential change in a distance between the sharp end and the sample. A second detecting unit detects a second detection amount relating to a change of the first detection amount. A control unit controls the distance between the sharp end and the sample in accordance with the second detection amount, so that an average value of the distance between the sharp end and the sample is brought close to a definite value.

Abstract: The invention pertains to level measuring by means of an oscillating fork (1) that is excited to oscillate by an oscillator circuit that, for example, is realized in the form of a series circuit consisting of an input amplifier (2), a band filter (3) and an output amplifier (4). An identifying element (6) is assigned to the oscillating fork (1), with the identifying element transmitting the fundamental frequency of the oscillating fork (1) to the oscillator circuit (2, 3, 4) in coded form. In addition, the identifying element (6) transmits the fundamental frequency of the oscillating fork (1) to the control input of a frequency evaluation circuit (5), the input of which is connected to the output of the oscillator circuit (2, 3, 4). Consequently, the parameters of the band filter (3), as well as of the frequency evaluation circuit (5), are optimally adjusted to the fundamental frequency of the oscillating fork (1).

Abstract: The microwave sensor produces an electrical output signal according to a position or displacement of a movable mechanical part (2), especially a valve needle in an injector valve for injecting fuel into an internal combustion engine. This position or displacement sensor includes a cavity resonator (40,70) provided with walls bounding a cavity (4,7) dimensioned for microwaves of a predetermined frequency and an antenna (8,14) for reception of the microwaves in the cavity. The end (3) of the movable mechanical part (2) protrudes into the cavity. A hybrid evaluating circuit (9) is connected with the antenna, which detects changes in the microwave radiation fed into and coupled out of the cavity, e.g. phase relationships, which depend on the position of the mechanical part (2), so that small position changes in very tight spaces are accurately determined.

Abstract: A measuring instrument and method for measuring paint and coating thickness on poorly conductive graphite substrates. The instrument uses a microwave amplifier, a measurement cavity, and an optional reference cavity with supporting electronics to measure the apparent changes in the length of the measurement cavity due to the changes in the paint and coating thickness. The measurement cavity resonates when the measurement cavity is set upon the test surface. The oscillating signal is sent through a) directly to a microwave frequency counter, or b) a reference cavity tuned to give the desired slope detection response to cover the paint and coating thickness range allowed. The filtered response of the reference cavity is converted to a dc level signal proportional to paint thickness. It is presumed that the expert user will have access to a PC allowing instant conversion—via a stepped calibration plate—to paint thickness in mils from electrical data.

Abstract: A measuring instrument and method for measuring paint and coating thickness on conductive and poorly conductive substrates. The instrument uses a microwave amplifier, a measurement cavity, and a reference cavity with supporting electronics to measure the apparent changes in the length of the measurement cavity due to the changes in the paint and coating thickness. The measurement cavity resonates when the measurement cavity is set upon the test surface. The oscillating signal is sent through a reference cavity tuned to give the desired filtered response to cover the paint and coating thickness range allowed. The filtered response of the reference cavity is converted to a dc level signal that serves as input to a data acquisition circuit. The data acquisition circuit converts the input signal to digital form so that the calibration method may be used to associate a given response with the corresponding paint and coating thickness.

Abstract: A method for determining the axial load on an elongate member by measuring the differences in time of flight for transversely and longitudinally ultrasonic waves introduced in the elongate member under a zero load condition and at a current temperature and the time of flight for both of these types of waves introduced into the elongate member under the actual load condition, and calculating from these differences in the time of flight the actual load on the elongate member taking into account the influence of any occurring difference in temperature of the elongate member between the zero load condition time of flight measurement and the actual load condition time of flight measurement.

Abstract: Method and apparatus for measuring distance includes a capacitance probe positioned adjacent a rotating member and within the housing of the rotating member such that the distance between the probe and rotating member can be measured. The rotating member and probe co-operate with each other so as to define a capacitor. An oscillator comprising a transmission line is electrically connected to the probe, the resonat frequency value of which is a function of the capacitance of the capacitor. The change in distance between the rotating member and the probe can therefore be measured.

Abstract: A system for determining the position of a piston moveable within a cylinder, or of an implement or joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter/receiver unit. The EM bursts are launched by the transmitter via a focusing antenna assembly from an end of the cylinder housing towards the piston. The fluid in the cylinder housing is in electrical communication with the piston such that a surface of the piston represents an electrical impedance discontinuity which causes the EM bursts to be reflected back to the receiver. The time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel back to the receiver via the antenna assembly is determined and converted into a position signal representing the piston's position. A compensation signal can be used to compensate the position signal for variations in a parameter of the fluid within the cylinder.

Abstract: The identification of and compensation for changes in the dielectric properties of a hydraulic fluid in hydraulic apparatus is achieved by continuously sampling a hydraulic fluid in a resonant chamber with a central conductor that is both inductively and capacitively coupled to an oscillator. The output frequency changes of the oscillator is an indicator of changes of the dielectric properties of the hydraulic fluid and their magnitude. The invention is of particular value in hydraulic cylinder piston position determining systems.

Abstract: A system for determining the position of a piston moveable within a cylinder, or of an implement or joint, is disclosed herein. Electromagnetic (EM) bursts such as ultra-wideband or frequency pulses are generated and applied to a transmitter/receiver unit. The EM bursts are launched by the transmitter along a transmission guide from an end of the cylinder housing towards the piston. The transmission guide can be a dipstick mounted within the cylinder housing or the cylinder housing itself. The dipstick or cylinder housing is in electrical communication with the piston such that a surface of the piston represents an electrical impedance discontinuity which causes the EM bursts to be reflected back to the receiver. The time for the EM bursts to travel from the transmitter to the piston and for the reflections to travel back to the receiver is determined and converted into a position signal representing the piston's position.

Abstract: A convenient, non-optical method for scanning probe microscopy tip-to-sample distance control based on the impedance change in a shear-force dither piezo. This is accomplished by determining the tip-sample distance by measuring the impedance change in a shear-force piezo-member. A Wheatstone type bridge can be utilized to regulate the tip-sample separation. Alternatively, an electrical bridge, having an output, regulates the tip-sample separation relative to the bridge output by driving the piezo/tip with a sine wave and combining said sine wave with a phase-referenced wave of equal amplitude at a 180.degree. phase shift. The electronic bridge detects impedance changes of about -100 dB across loads with impedance phases between -90.degree. to +90. Power dissipation is determined by measuring changes in electric impedance that a dither piezo presents to an oscillator.

Abstract: An apparatus for determining the position of a work implement relative to an earthworking machine. An antenna is mounted to the machine and is oriented to transmit a high frequency signal toward the implement and receive a reflected signal back from the implement. An oscillator is electrically coupled to the antenna and energizes the antenna with electrical energy to generate the high frequency signal. The oscillator produces an output signal having a frequency responsive to the inductance of the antenna. A microprocessor based circuit receives the output signal of the oscillator and responsively determines the position of the work implement relative to the machine. The position of the work implement is a function of the frequency of the output signal.

Abstract: A piston position sensing system with improved accuracy and reliability is achieved by electromagnetic wave coupling using the combination of: a mechanical structure that in addition to supporting the rod, provides an extension of the resonance cavity, supports the electromagnetic wave couplers and a hydraulic fluid input-output port into the extended cavity and a piston travel stop; an electronic circuitry shielded package having a high frequency section with coaxial shielded input and output conductors on opposing package sides and a lower frequency counting section having a piston position output shielded conductor and a fluid dielectric property change monitor input conductor separated from the high frequency section conductors; and, the positioning of the electronic package on the mechanical structure with the coaxial shielded input and output conductors respectively adjacent to the input and output couplers and with the hydraulic fluid input-output port positioned elsewhere around the periphery of the c

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 method of inspecting an abnormality occurring inside a pipe to be inspected, and an apparatus for practicing the method, which includes the steps of transmitting an electric radio or radio frequency (RF) wave having a predetermined frequency from an antenna of a transmitter located at a predetermined position inside the pipe, receiving the transmitted RF wave by an antenna of a receiver located at a predetermined position inside the pipe, and discriminating a characteristic of the received RF wave. The characteristic of the received RF wave can be the intensity of the RF wave, and an attenuation amount is detected in a first example. Alternatively, the characteristic of the received RF wave may be the time required to reflect the transmitted RF wave and receive it with the receiver, and the time interval between transmission of the RF wave and reception of the reflected RF wave is measured in this alternative.

Abstract: A piston position sensing system in which tabulated resonance width related information is stored in a form correlated with piston travel so that measured resonance width information can be compared with the stored information in determining piston position and compensation for the velocity of the piston is provided by correction for a time difference in serial sensing between the initial and the following extremes of a resonance signal as the piston moves. the compensation is developed from velocity information identified through previous and current processing cycles which assures reliability in detection of the subsequently sensed portion of the resonance signal envelope and enhanced sensitivity and accuracy through automatic application incrementally in a dynamic gain adjustment of the sensing system.

Abstract: An embodiment of the present invention is a roadway sensor for surface installation in a hole such that a thin ceramic contact sensor may be used to measure and cross-compare fundamental physical antenna parameters of the space immediately above a roadway or bridge surface. Measurements are combined by a microprocessor to discriminate between dry pavement, water (rain), snow and ice above the sensor head. Ambient surface temperature, water depth and ice/slush conditions are determined to estimate any hydroplaning hazard and ice/antifreeze/water mixtures. The sensor comprises an antenna that exhibits a resonant frequency and an input admittance including a real term; a Maxwell bridge coupled to the antenna for detecting the resonant frequency, input admittance and real term; and a frequency sweeping oscillator for driving the antenna at a plurality of frequencies proximate in frequency to the resonant frequency.

Abstract: Improvement of the ability to detect selected resonant frequencies associated with the position of the piston in a piston position sensing system using electromagnetic waves in the fluid in a hydraulic cylinder is achieved by positioning the electric signal input and output probes with 90 degree separation around the circumferential periphery of the cylinder to suppress coupling into unwanted modes that diminish detectability of particular resonant frequency signals, In a coaxial sensing system "dummy" probes at 90 degree separation to each other and 90 degree separation to the input and output probes operate to improve symmetry and resonance shape and to suppress unwanted modes.

Abstract: A method of measuring the inner diameter of a pipe includes the steps of continuously transmitting RF waves of a predetermined frequency band from an antenna of a transmitter located inside of the pipe to be inspected, receiving the RF waves with an antenna of a receiver located inside the pipe, the antenna of the receiver being spaced apart from the antenna of the transmitter by a predetermined distance, detecting a frequency at a change point where an intensity of the received RF wave changes greatly, and substituting the frequency at the change point into a formula: d=c/1.706f (wherein d is the inner diameter of the pipe, c is the velocity of light, and f is the frequency at the change point) which shows the relation between the inner diameter of the pipe and the frequency to obtain a minimum inner diameter of the pipe.

Abstract: A device for injecting current at radio frequency into electric wiring, comprises a guiding structure (10) of an electrically conductive material consisting of a tapered shell (12) wherein a central vertical wall (20) is suspended determining two half-spaces (S, D) within the shell (12). At the tapered end, the shell (12) and the central vertical wall (20) are respectively connected to the braiding and the central wire of a coaxial cable (17) supplying radio frequency electric current. At the end opposite to said tapered end, a wiring (19) is disposed through the structure (10) perpendicular to the vertical central wall (20) and rests on a base (11) of dissipating material. In one of the two half-spaces, the wiring (19) is protected by a shield (23) integral with the shell (12).

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 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.