Abstract: A method and device for ultrasonic ranging. As in prior art devices, ultrasound pulses are transmitted by the device towards a target, and echo pulses from the target are received. The timing of the maximum of the amplitude envelope of the echo pulses is picked and used as a measure of the return time of these pulses. This maximum envelope time is relatively independent of the speed of sound between the device and the target. Preferably, the duration of the echo pulses is less than the response time of the receiving circuit, to enable an accurate pick of the amplitude envelope maximum.

Abstract: In a method for determining the position of an object relative to the background with ultrasound, a plurality of ultrasound transducers arranged in a row simultaneously transmit ultrasound in line-shaped fashion in the direction of an object scene and receive both the echo of the signal transmitted by the transducer itself as well as the echoes of the signals generated by the neighboring ultrasound transducers. On the basis of a reference measurement wherein no object is located in the measurement region, the amplitudes and the times of incidence of the echo signals are stored. In the following measurements with an object, the echo amplitudes and the times of incidence of the echo signals are again stored and compared by fuzzy logic to those of the reference measurement. As a result, this supplies the position of the object relative to the background.

Abstract: A digital signal processor wherein a bit stream containing correlation inmation for a large sample size is converted into several basic correlation functions, each of which covers a small number of samples within the large input sample. Each basic correlation function is examined to determine whether it contains a valid sonar signal, and the original bit stream is then integrated over those time periods for which the corresponding basic correlation functions indicate the presence of a valid sonar signal. The resulting optimized digital correlation function is converted into an analog signal.

Abstract: A scheme for filtering noise from a signal, in which the noise fluctuates significantly in phase. The signal is sampled to produce N members of a time series and the phase of each signal extracted in the form of a magnitude and a phaser, i.e. for a time series .vertline.x.sub.1 .vertline.e.sup.i.theta..sbsp.1, .vertline.x.sub.2 .vertline.e.sup.i.theta..sbsp.2, . . . , .vertline.x.sub.N .vertline.e.sup.i.theta..sbsp.N, where .vertline.x.sub.n .vertline. is the magnitude of the nth member of the N time samples, and e.sup.i.theta..sbsp.N the phaser for the nth sample. The phasers are added to form a complex value s such thats=.SIGMA..sub.N=1.sup.N ?Re(e.sup.i.theta..sbsp.n)+iIm(e.sup.i.theta..sbsp.n)!.Phase noise which fluctuates strongly will tend cancel itself in the sum s, whereas phase resulting from a stable signal will tend to reinforce. Thus the scalar .vertline.s.vertline.

Abstract: An ultrasound transducer head that contains at least one transducer element, which receives ultrasound signals and converts them into electrical receive signals, and an amplifier device, which electrically amplifies the receive signals of the transducer element. The amplifier device contains at least one capacitive component, preferably a controllable capacitive diode. The gain of the amplifier device can be varied as a function of the capacitance of the capacitive component. A virtually loss-free gain is obtained over a large dynamic response range.

Abstract: The invention provides a process and apparatus for the detection of obstacles by means of ultrasound waves having an enhanced ability to distinguish between echoes caused by obstacles and those caused by interference signals. Ultrasound pulses are emitted by an ultrasound transmitter unit, and are received by an associated ultrasound receiver unit. (A plurality of such transmitters and receives may also be used.) Ultrasound echoes detected by the receiver units are used to form echograms in which detected echoes are projected. The echogram thus measured is used to generate an analysis echogram, based on information contained in the measured echograms. In particular, the most recent analysis echogram is modified depending on the size and location of echoes contained in the measured echogram. Signals contained in the analysis echogram are then compared with predetermined threshold values to distinguish between echoes reflected from obstacles and echoes due to interference.

Abstract: A method for detecting radiated and reflected acoustic signals from an unwater source, wherein the acoustic signals are present in a random noise environment and form an output therewith. The method includes the steps of operating an entropy-based acoustic receiver to receive the output, calculating the entropy of the received output, and comparing the calculated entropy with a selected entropy threshold value. A substantial difference is indicative of the presence of an acoustic signal from an underwater source. A less than substantial difference is indicative of a lack of presence of an acoustic signal from an underwater source.

Abstract: A device for the measurement of distance with ultrasound is provided in which a transmitter emits a pulse-type signal which is reflected and is converted into an electrical echo signal in a receiver. The distance between transmitter and receiver is determined by measuring the transit time between the emitted and the received signal. Since the level of the echo signal as a function of the emitted signal depends on the characteristics of the reflector and on the distance between transmitter and receiver, inaccuracies may occur in the evaluation of the echo signal and these are avoided by varying a switching threshold or by varying the amplification of the echo signal or by modifying the radiated signal as a function of the previously received echo signal.

Abstract: The present invention relates to a method and apparatus for measuring distance to an obstacle which can be equipped to a self-propelled robot, and more particularly to a method and apparatus for measuring distinct to an obstacle which can improve distance resolution not by relying on an analog-to-digital conversion time but by relying on a system clock (main clock). The invention can distinguish noise by varying a reference voltage in order to discriminate whether the same is the signal reflected from the obstacle and received thereform, and can distinguish an accurate measurement by mutual comparison after measuring the distance by way of the two methods to thereby detect accurately the distance to the obstacle.

Abstract: A method and apparatus for controlling the false alarm rate of a receiver which detects each received signal having a power level greater than a predetermined threshold level which is received within a predetermined detection interval. The receiver is adapted to receive signals in response to source signals having a predetermined transmission period. The signals detected within each transmission period can include an initial signal and a plurality of excess signals received subsequent to the initial signal. The total number of detected signals and the number of excess signals received within the predetermined detection interval are counted and a ratio therebetween is determined. Based upon the ratio of the total number of signals to the number of excess signals, the relationship between the power level of the received signals and the threshold level is adjusted in order to control the false alarm rate of the receiver.

Abstract: A system for facilitating the tracking of a target vehicle in connection h successively-received acoustic sensor signal data items. A fast Fourier transform operation is performed in connection with each successive acoustic sensor signal data item to generate a phase and amplitude beam map reflecting spectral signal energy in the received acoustic sensor signal data item. If the beam map for a acoustic sensor signal data item indicates that the item represents a signal having a signal-to-noise ratio above a first predetermined threshold value, a beam map generated for a previous acoustic sensor signal data item is used to generate a bounded beam map, a determination is made as to whether the bounded beam map represents a signal having a second predetermined signal-to-noise ratio. In response to a positive determination for the latter signal-to-noise determination, both the beam maps are used to generate tracking information for the target vehicle.

Abstract: The invention provides a generally noninvasive device and method for detecting a reciprocative piston located within a cylinder bore. An ultrasonic transducer mounted on the outside of the cylinder wall selectively generates an ultrasonic transmission signal directed through the cylinder. The transducer then receives any desired ultrasonic signal produced by propagation of the ultrasonic transmission signal. Control circuitry processes electrical signals produced on the ultrasonic transducer by the propagated ultrasonic signal to indicate presence or absence of the piston.In presently preferred embodiments, the control circuitry determines whether the piston is present by comparing a signal level in the received ultrasonic signal during a sample time window in which the desired signal may be expected with a predetermined threshold level. To perform this function, electrical signals produced on the transducer by the propagated ultrasonic signal are first passed to an amplifier having a selected gain.

Abstract: The invention provides a generally noninvasive device and method for detecting a reciprocative piston located within a cylinder bore. An ultrasonic transducer mounted on the outside of the cylinder wall selectively generates an ultrasonic transmission signal directed through the cylinder. The transducer then receives any desired ultrasonic signal produced by propagation of the ultrasonic transmission signal. Control circuitry processes electrical signals produced on the ultrasonic transducer by the propagated ultrasonic signal to indicate presence or absence of the piston.In presently preferred embodiments, the control circuitry determines whether the piston is present by comparing a signal level in the received ultrasonic signal during a sample time window in which the desired signal may be expected with a predetermined threshold level. To perform this function, electrical signals produced on the transducer by the propagated ultrasonic signal are first passed to an amplifier having a selected gain.

Abstract: In an ultrasonic measuring apparatus for emitting an ultrasonic pulse, receiving reflected echos and producing an echo signal representative of the echos resulting from each impulse, each echo signal has a first portion corresponding to echos from one group of interfaces and a second portion corresponding to echos from another group of interfaces. The apparatus comprises a gain control (24) for controlling the amplitude of each echo signal and a processor (26) for receiving and treating said echo signals.

Abstract: A multistatic sonar system (50) employing a short duration automatic gain control (AGC) following beamforming of the return signal to reject spatial transients at the sonar waveform leading and trailing edges. The output of the beamformer (58) is delayed by a delay line (60A) before passing through a programmable gain (60B). The magnitude of an undelayed version of the beamformer output is also squared (60D) and averaged over a time window (60E). This average is used to normalize the delayed value of the beamformer output. The normalized output of the beamformer is compared (60C) with a threshold having a value much greater than unity, and the comparator output controls the gain circuit (60B). When the normalized value of the beamformer output exceeds the threshold value, the gain of the AGC is set to a value much smaller than unity. When the normalized value of the beamformer output does not exceed the threshold, the gain of the AGC is set to unity.

Abstract: Individual elements of a sonar receiver transducer provide output signals in response to the receipt of acoustic energy and signals are processed to form one or more receiver beams for display. Each element output is provided to a preamplifier to which is applied a time varied gain function. The output signal of at least one of the preamplifiers is additionally provided to an adaptive time varied gain circuit which generates an error signal for correction of the time varied gain function applied to the preamplifiers.

Abstract: A method and circuit for performing coherent integration on a signal output rom a conventional signal processing circuit's detector/averager is presented. The post-processing coherent integrator is designed to be inserted in a conventional signal processing circuit between the detector/averager circuit and the threshold detector circuit.A digital form of the post processing coherent integrator comprises a sample-and-hold circuit to receive a signal output from the detector averager of the conventional signal processing circuit, an analog-to-digital converter, a delay and multiplier circuit, a memory circuit for storing weighting constants, a summer circuit, and an output to a conventional signal processing system's threshold detector and display.

Abstract: Apparatus and methods for improving signal detection and tracking in underwater acoustic devices receiving a set of acoustic pulses propagated in response to repetitive synchronizing events. Each of the set of pulses is correlated with a replica of each pulse in a receiver in the underwater devices during an associated time window. The correlated output of the receiver is compared to an adjustable threshold characteristic in a detector for selection of the actual pulse according to predetermined criteria for each of the set of pulses. An actual time of reception relative to the synchronizing event is assigned to the selected pulse. Previous actual times of reception are used to estimate the expected time of reception of the associated pulse relative to the next synchronizing event. The estimate is used to adjust the associated time window to encompass the expected time of reception.

Abstract: For the measurement of distance using the pulse transit time principle the received signal produced after each transmission of a pulse is stored as an echo profile and the effective echo is determined from the stored echo profile. In order to suppress recurrent interfering signals a stationary threshold profile adapted to the measurement environment is formed and employed for each evaluation of a stored echo profile. In order to take into account fluctuations in the properties of the received echo profile rapidly without necessitating a modification in the stationary threshold profile for this, from a stored echo profile a floating threshold profile is generated in the form of a monotonously descending curve. From the mutually corresponding values of the floating threshold profile and of the stationary threshold profile the respectively larger value is utilized for the formation of a resulting threshold profile, which is employed for each evaluation of stored echo profiles.

Abstract: A time-of-flight range sensing system for a vehicle such as a mobile robot comprised of a number of sensors that are situated at preset locations and aligned with particular orientations on the vehicle. Each sensor may consist of single or multiple transmitting transducers and single or multiple receiving transducers. Each sensor provides a means for changing the effective sensing volume of the sensors or it has two or more separate processing channels for processing the time-of-flight information with several different effective sensing volumes using the sensor signal processor. The sensor signal processor also provides a means for collecting information regarding the echo signal peak value and the noise present in the received signal before reception of the first echo.

Abstract: A device to warn a ship crew of submerged objects in their immediate vicinity, combined with alarm and logging facilities. The device is composed of one or more sonic or ultra sonic transducers placed aboard the ship, with coverage arranged so as to give surrounding "envelope" to the sides and to the area ahead of the vessel, as well as some predetermined downward looking angle. The transducer or transducers are connected to an electronic distance measuring device that will measure distance to possible obstacles, similar to conventional sonar techniques. The measurements in each direction are compared by an electronic processor against a table of minimum distances, and if the distance falls below the predetermined value for a given direction, an alarm is activated. In addition, all alarms, cancellations of alarms, activation and deactivation of the system are logged automatically with an identification of the operator.

Abstract: The present invention shows a system for the continuous echo analysis of a body of liquid, surrounded by walls of known dimension, for the presence of an object. Such a system comprises:a transmitting component capable of translating an electrical pulse into intermittent instigative pulses of sonic energy emitted into the body of liquid, wherein such pulses of sonic energy permeate the body of liquid, reflecting off the walls and any object within the body of liquid, and returning as a set of echo information;a receiving component capable of receiving such echo information and translating that echo information into a waveform equivalent of that echo information; and,an analysis component comprising a microprocessor-controlled electronic circuit capable of receiving each waveform and comparing that waveform against stored data on previous waveforms to provide an alarm activation signal when the variance exceeds a predetermined settling.

Abstract: A side-looking fish finding apparatus transmits a sonar pulse approximately horizontally into a body of water, and then monitors echoes from the pulse. The time interval between successive sonar pulses is varied in a random manner in order to permit two or more similar units to be used in close proximity to each other without significantly interfering with each other. An individual echo is treated as the detection of a fish if it has a magnitude above a predetermined threshold, if it has a length within a predetermined range bounded by upper and lower limits, if it is preceded by a leading space interval free of other echoes and having a predetermined duration, if it is followed by a trailing space interval free of other echoes and having a predetermined duration, the duration of the trailing space interval being less than the duration of the leading space interval, and if an equivalent echo is received in response to each of the next four successive sonar pulses.

Abstract: The uncertainty inherent in high-resolution acoustic pulse-echo distance measuring systems which depend on threshold detection is overcome by transmitting a multi-cycle shot of acoustic energy having a sharply peaked amplitude profile, and locating the peak amplitude of a received echo. The peaked amplitude is achieved by timing the duration of energization of a transducer producing the shot so that energization is terminated before the amplitude of oscillation of the transducer has reached a maximum. This produces a shot which has a definite largest cycle, which should in turn produce an echo having a definite largest cycle.

Abstract: A system for monitoring level of material in a vessel that includes a transducer for transmitting an ultrasonic signal toward and receiving an echo signal from a surface of the material, and a power switch coupled to the transducer for energizing the transducer to transmit the ultrasonic signal. A microprocessor-based controller has an output coupled to the power switch for controlling operation thereof. The output of the microprocessor provides a pulsed periodic signal to the power switch at controllably variable frequency, duty cycle and/or total burst duration to operate the transducer at an ultrasonic frequency that corresponds to the periodic signal frequency, duty cycle and burst duration. The echo signals are compared to successive thresholds between the transmission bursts, and echo signal data is sampled and stored in the microprocessor over a measurement cycle that includes multiple transmission bursts.

Abstract: An ultrasonic level detector includes a transducer for generating and receiving bursts of sonic energy at a surface to locate the position of the surface. In response to receiving a burst of energy reflected from the surface, the transducer generates an electrical signal, which is then supplied to a variable gain amplifier. After amplification, the electrical signal is supplied to a comparator and a peak detector. The comparator generates a timing signal upon the electrical signal exceeding a threshold. A window generator circuit generates a receive window that controls whether the electrical signal is supplied to the comparator and the magnitude of the threshold on the comparator. The peak detector determines the maximum amplitude of the electrical signal, which may be used to vary the amplifier gain and the number of pulses included in an excitation signal which drives the transducer. Upon receipt of the timing signal, a microprocessor determines the distance between the transducer and the detected surface.

Abstract: This invention relates to a method of, and apparatus for, detecting the position of an object relative to a detector device, in which a pulse signal is transmitted to such object by a transmitter means, and a receiver means receives a signal reflected by the object, the position of the object being determined in dependence upon the time difference between the moment the transmitter means transmits the pulse signal and the moment the receiver means receives the reflected signal. According to the invention, to eliminate the effect of spurious signals, a reference signal stored in a memory means is subtracted from the signal received by the receiver means, which reference signal has previously been received by the receiver means in response to a signal transmitted by the transmitter means in the absence of an object whose position is to be detected.

Abstract: A phased array sector scanning ultrasonic imaging system produces digitized baseband samples of the received ultrasonic echo signals amplified by a time gain control (TGC) to compensate for dispersion losses in the media in which the ultrasonic signals propagate. A time frequency control filter employs the same TGC control signal to calculate a phase shift correction as well as the coefficients which determine the characteristics of a bandpass filter such that the frequency dependent dispersion losses in the ultrasonic echo signals are compensated.

Abstract: The invention provides a method of and apparatus for determining if a newly reported target is correlatable with target tracks already stored in a data base. Correlation is effected in stages rejecting uncorrelatable stored target tracks and accepting closely correlated target tracks and includes decision applying means for accepting a stored target track as a correlated track only under stringent conditions.

Abstract: A method of measuring a distance to an object includes generating first signal pulses to be bounced off the object and receiving the first signal pulses, after the first signal pulses have been bounced off the object, as second signal pulses. When the amplitude of the second signal pulses is above a predetermined value, the second signal pulses are differentiated and then supplied as differentiated second signal pulses to an input of an analog-to-digital converter. When the amplitude of the second signal pulses is not above the predetermined value, the second signal pulses are passed through to the input of the analog-to-digital converter unchanged. Signal pulses at the input to the analog-to-digital converter are converted into digital signals. The digital signals are summed over a period of time to generate a sum. The sum is used to determine the time delay between generating the first signal pulses and receiving the second signal pulses. The time delay is proportional to the distance to the object.

Abstract: This invention relates to a distance measuring device, in particular for motor vehicles, in which a converter is utilized for transmission of an ultrasonic signal and also for reception of the echo signal. Thereby the echo signal received by the converter is compared at a comparator with a threshold value after having been appropriately amplified. This threshold value is at a particular changeover time changed over from a first high value, which is independent of time, to a smaller, time-dependent value. Thereby the changeover time is computed from a measured time depending on the dying-out behavior of the converter.

Abstract: This invention provides an improved circuit for dynamically controlling a predetermined characteristic of each input channel of a system having a plurality of input channels to achieve a desired characteristic profile with predetermined time variances in channel aperture size and/or focal point depth. More particularly, the invention dynamically controls the gain of each input channel to maintain a desired apodization profile. A plurality of basic time varying functions (basis functions) are generated, such functions being, for example, a constant, a ramp, a parabola an exponential or the like, and at least selected ones of the basis functions are combined by appropriately weighting the functions and adding the weighted functions to obtain a desired control signal. The control signal which has the desired dynamic gain characteristic for the given channel is then applied to control a gain-controllable amplifier for such channel.

Abstract: An ultrasonic obstacle sensor for sensing an obstacle on a road surface is disclosed which projects ultrasonic waves in the form of pulses toward the forwardly distant surface of a road in a downwardly inclined forward direction, and which is able to discriminate an obstacle on the road surface through reflection waves therefrom in a most effective and reliable manner. To this end, a timing instructor intermittently generates an instruction signal, based on which ultrasonic waves are generated. An ultrasonic transmitter projects the ultrasonic waves thus generated toward a road surface, and the reflected waves therefrom are received by an ultrasonic receier which in turn generates a reception signal. A reception signal processor AM detects the reception signal to provide an AM modulation signal. A time calculator calculates a time elapsing from the generation of the instruction signal.

Abstract: A distance sensing system includes an ultrasonic transducer, a transceiver and a microcontroller-based signal processing unit. The transducer periodically generates and directs towards the terrain a dual frequency ultrasonic signal. Echo signals from the ground and/or any intervening crop or trash are reflected back to the transducer and are processed. The system generates amplified and filtered echo envelope signals. Leading and trailing edge times are determined as the times the echo signals cross a threshold value which is a certain proportion of a maximum echo amplitude value. A near distance value is derived from the leading edge time of the first echo which exceeds a minimum amplitude. A far distance value is determined as the trailing edge time of the last echo signal which has an amplitude which exceeds a certain value. Multiple echo time and amplitude values are derived from the maximum amplitude echo.

Abstract: For detecting a quickly or sharply varying signal (the event) against a background of a more slowly changing ambient signal (the background), the envelope detector inputs the signal and full wave rectifies it. It sends the signal to the background filter and event filter, each of which includes an RC circuit. The background filter and event filter each independently process the signal to be evaluated in different manners based on the intrinsic frequency characteristics of the event signal, and of the background signal. The outputs of the two filter sections are sent to the decision section. Based on its processing, the decision section outputs a signal in one of two states, one corresponding to detection, and the other corresponding to non-detection.

Abstract: An acoustic signal receiving and processing circuit provides an output signal that enables a distance to be determined between a transmitter and a sensor. The circuit comprises a sensor which receives both noise and acoustic position signals, the acoustic signals arriving after a time delay indicative of distance between the signal's transmitter and a sensor. A level control circuit provides a plurality of output potentials, one of which is a ramp signal and another is a neutral voltage, the ramp signal produced in response to a start signal manifestation. A comparator circuit, has a pair of inputs connected to the level control and sensor circuits, respectively. The comparator circuit produces a first output signal in response to a potential on one of its inputs exceeding a potential on another of its inputs, i.e. when a voltage transition of a received acoustic signal initially passes a voltage manifested by the ramp signal.

Abstract: The disclosure is directed to an apparatus and method for determining the travel time of acoustic energy over an unknown travel distance between an acoustic transmitter and an acoustic receiver. This information can be used, for example, to determine the position of a moveable element in a data space. A timer is initiated at the time of acoustic transmission from the transmitter. A control signal generator is provided, and is initiated at the time of acoustic transmission from the transmitter, the control signal being a function of the time which elapses after the time of acoustic transmission. The gain of the signal received at the receiver is controlled in accordance with the control signal. The timer is terminated when the gain-controlled received signal exceeds a predetermined threshold. In a preferred embodiment, the terminating means includes a comparator for comparing the gain-controlled received signal to the predetermined threshold.

Abstract: A rotary ultrasonic transducer logging tool is set forth which has a transmitter connected to a transducer for transmitting pulses periodically, and a rotor with angle sensor connected thereto. One full revolution is divided into a specified number of incremental steps. The output of the receiver is supplied to an automatic gain control amplifier, then to an analog to digital converter. A gain control setting for the AGC amp is included. The AGC setting for the particular corresponding points in a first revolution of the transducer are used to provide settings for the AGC amplifier in the next revolution. A first buffer is used to store the data for the first revolution, a second buffer for the second revolution, and alternately back to the first buffer. These two buffers provide an output signal for a gain control buffer then input to the AGC amplifier. Alternate forms of gain control signal selection are used such as prior gain control settings.

Abstract: In acoustic level sensing apparatus, in which pulses of acoustic energy are transmitted by an electrically energized transducer towards a surface to be sensed, and the electrical output from the transducer following the pulse is digitized and analyzed to detect a return echo from the surface, so as to produce a digitized echo profile. The digitzed echo profile is enhanced by removing narrow peaks likely to correspond with certain types of spurious echo, and narrow valleys which may represent fragmentation of a wanted echo. Echoes are identified by comparing the profile with a time varying threshold generated derived from a linear regression performed on part of the threshold, various different types of comparison being performed and their results combined prior to selecting the most likely true echo on the basis of the combined results.

Abstract: A microprocessor-based ultrasonic intrusion detection system includes an initialization mode wherein a plurality of echoes are cumulatively processed to produce a reference or signature data set representing the area to be monitored without intruding objects. Later received echoes are compared to this signature so that an intruding object will cause generation of an alarm signal. Time varying thresholds are utilized to compensate for attenuation caused by increased distance.

Abstract: A target tracking sonar system associated with a moving platform incorporates a Kalman filter model and a false target detection capability characterized by comparison of the estimated and actual acceleration to produce an error value which, if greater than a predetermined threshold, namely the product of one half the estimated acceleration and the internal between periodic acceleration updates, generates a signal condition to flag the false target.

Abstract: An acoustic ranging apparatus directs a burst of acoustic energy toward an acoustically reflective target object. The time it takes for an echo to return to the ranging apparatus is measured to determine the distance between the ranging apparatus and the object. The echo is received, amplified, and compared with a threshold voltage which decays in time in a manner which simulates the attenuation of acoustic energy as a function of distance travelled in the medium. The attenuation function is substantially simulated over the distance range that the ranging apparatus is intended to accurately measure by means of a simple, low cost first order linear circuit. The ranging apparatus responds only to echoes having a magnitude which exceeds the threshold voltage. Suprious or false echoes, such as those due to reflection of acoustic energy in the side lobes produced by an acoustic energy transducer in the ranging apparatus, are ignored.

Abstract: A method for suppressing interference signals during operation of ultrasonic proximity transducers suppresses the interference signals that are generated by continuous noises. Repeated ultrasonic pulses are transmitted from an ultrasonic proximity transducer, and the received signals are scanned. The scanned values of the received signal are converted into digital values. After storage, the digital values are compared with a step function having one or more step sections of constant value serving as a time-dependent interference noise threshold so that the usable echo signal can be determined and separated from the interference signals. With further evaluation, the echo transit time of the usable echo signal is determined and provided to a control and evaluation unit. By suppressing continuous noises, and further suppressing stochastic interference signals, the usable echo signal is reliably filtered from a reception signal that is overlaid with interference signals.

Abstract: An apparatus for determining the length of an open or closed-end pipe by measuring the propagation delay of a sound pulse transmitted down the pipe bore. The apparatus includes an acoustic transducer, an acoustic detector and associated circuitry for computing the time required for an acoustic pulse to travel and return the length of a pipe. Electronic circuitry, including a microprocessor, is employed to provide the apparatus with an automatic gain adjustment feature. The gain circuitry increases the amplification until a return pulse of desired amplitude is obtained. The gain is time varying to make the last-to-return signals strongest thereby avoiding false readings from pipe discontinuities. Compensation is made for speed-of-sound variations due to temperature, humidity, and barometric pressure by direct measurement of speed of sound during each length measurement. The open or closed endedness of a pipe is determined by return signal charateristics and a correction factor applied for open-ended pipe.

Abstract: In combination with any signal processor system which uses an R-C integra type energy detector to recognize the presence of electrical signals such as those that are proportional to a received acoustic ping signal, the turnaround time stability improvement comprising a timing initiation signal recognition means, a validation means, first and second one-shorts for A/D conversion, and AND gate means for receiving the timing initiation signal and the validation signal and outputting a valid ping timing signal only when both are true, said valid ping timing signal in turn causing subsequent actions normally initiated by this event to occur, such as a transponder system incorporation the present invention projecting a return ping into the water.

Abstract: In acoustic level sensing apparatus, in which pulses of acoustic energy are transmitted by an electrically energized transducer towards a surface to be sensed, and the electrical output from the transducer following the pulse is digitized and analyzed to detect a return echo from the surface, so as to produce a digitized echo profile. The digitized echo profile is enhanced by removing narrow peaks likely to correspond with certain types of spurious echo, and narrow valleys which may represent fragmentation of a wanted echo. Echoes are identified by comparing the profile with a time varying threshold generated derived from a linear regression performed on part of the threshold, various different types of comparison being performed and their results combined prior to selecting the most likely true echo on the basis of the combined results.

Abstract: An improved microprocessor-controlled sonar depth sounder, which is automatically operative to detect and lock to the bottom of a body of water, fill in the display below the detected bottom, change display scales in response to the detected bottom going off-scale, and reformat the entire display in response to a scale change. A memory is provided for storing target data up to the operable depth limits of the device, thereby allowing display reversing and display expansion or "zoom" of a predetermined portion of the display selected by a zoom cursor. The zoom or cursor is variably positionable at different depths. The device employs an improved variable sensitivity amplifier. Also disclosed is an improved water-resistant switch construction for marine electronic equipment.

Abstract: An ultrasonic, echo-ranging instrument for measuring liquid level, the instrument including a transducer dispoed at a fixed position directly above the liquid surface. The transducer is excited to emit periodic pulses which are intercepted by the liquid surface as well as by a reference point a fixed distance from the transducer to produce both reference and liquid echo pulses that are returned to the transducer and detected thereby. The respective transit times of the reference echo and the liquid echo pulses are determined, and the ratio between these transit times is computed to provide an output representing the level of liquid. To ensure accurate readings, the reference echo and liquid echo pulses from the transducer are fed to a single automatic gain control circuit whose operation is time shared.

Abstract: The electrical response of a transducer contains a data-providing signal or signals superimposed on an unwanted time-variable background signal which is independent of the data-providing signal or signals. A system processing the transducer response utilizes an electronically stored digital simulation of the background components whereby combination of the transducer output with the digital simulation, after digital to analogue conversion of the latter, substantially frees the transducer output of the background component to facilitate detection of the data-providing signals.

Abstract: An apparatus and method for determining the position of an object, especially the position of a movable object in an industrial vessel. The position is determined by the use of two signals having a very large difference in their velocities, such as electromagnetic and acoustic waves. The object whose position is to be determined receives the electromagnetic signal, analyzes the electromagnetic signal, and, if appropriate, transmits an acoustic signal. In addition to the object containing an electromagnetic receiver and an acoustic transmitter, there is required an electromagnetic transmitter, three or more receivers to receive the acoustic signal from the object, and supporting equipment to process signals and log data. When the object transmits an acoustic signal, the acoustic receivers, which are in known positions in the vessel, receive the signal at different times depending on the distance of the object from each receiver.