Abstract: Methods and apparatus for calibrating terminated ultrasonic electroacoustic transducers are disclosed. The transducers are excited by a driving signal to emit an ultrasonic acoustic wave, which wave is received either by the same transducer after reflection or by a second transducer to produce an output signal. The driving signal and output signal are supplied to measuring circuitry deriving transdBACKGROUND OF THE INVENTIONThe invention described herein was made in the course of work under a grant or award from the Department of Health, Education and Welfare.

Abstract: The coagulometer for measuring the clotting time of liquids such as blood has a turning sample vessel whose axis of turning is at an angle to the vertical. Within the vessel an annular space is formed. The amount of liquid to be tested placed in the annular space is such that no complete ring stretching right the way round the axis of turning is formed when the vessel is not being turned or is being turned before clotting has started. When however clotting takes place sample liquid is transported up the sloping lower face of the annular space, such motion being sensed by a recording system.

Abstract: An ultrasonic testing method permits investigating the nodal point in the profile of a cast wheel of a motor vehicle between clinch and wheel flange. Hollow spaces occurring in this area may be tolerated when the remaining wall thicknesses between the profile legs do not drop below a certain thickness. In order to be able to check a wheel in one single measuring process and with a simple measuring geometry, two of the three intermediate leg parts are tested by direct testing by an evaluation of the echo height in consequence of lateral contraction of ultrasonic energy or in consequence of partial reflection which allows one to make conclusions with regard to the cross section and sound spots of the material through which ultrasound was sent, while the remaining part is measured by means of a simple travel time transversely to the residual wall. An apparatus for performing this method is disclosed.

Abstract: Process and apparatus for determining visco-elastic characteristics of specimens such as fluids and/or of polymerizing mixtures, especially of coagulation fluids such as blood or blood plasma, and their temporal changes by determining the resonance frequency and/or the amplitude of the resonance frequency of the oscillation system formed by a member and its elastic support which are stimulated for oscillation over a frequency range at least close to the natural or Eigen-frequency of the oscillation system. That member which is so stimulated is either a specimen container or a body therein, the other being fixed, so that there is relative motion between them. The determined resonance frequency amplitude relates to the viscosity of the specimen, while the position of the resonance frequency relates to the elasticity of the specimen and thus to the total elasticicty constant of the oscillation system.

Abstract: An apparatus for measuring or observing parameters representative of the coagulation and/or the lysis of a coagulable liquid, such as blood, comprises a torsion thread, a driving body supported by the torsion thread to be dipped in the liquid, a vessel containing the liquid is oscillated with a predetermined angular amplitude and period around an axis substantially identical with the torsion thread.Detection means comprise an inductor driven by the thread and a fixed position-detector which delivers an electrical signal representative of the amplitude of the oscillations of the torsion thread.The torsion thread is constituted by a wire stretched between two anchoring points and bearing the mass.

Abstract: An elastometer for measuring the mechanical strength of biological gels such as blood or fibrin clots. Thus this device may be used for accessing anticoagulant and fibrinolitic activities, particularly with respect to drug evaluation. The instrument can also be used to study abnormalities in the blood clotting process, i.e. for clinical diagnosis purposes.

Abstract: An ultrasonic scanner for use in medical diagnosis which produces two different types of scans. The scanner includes a housing carrying one or more ultrasonic transducers which traverse an arcuate path. A first reflector is positioned within the arcuate path to intercept ultrasonic waves and converge them at a point beneath the scanner in order to produce a skin centered sector scan, which is useful for viewing through small acoustic windows such as intercostal regions. A pair of reflectors, one of which is positioned horizontally with respect to the first reflector and the transducers, are utilized to form a wide aperture sector scan which diverges upon exiting the scanner housing. The wide aperture scan is useful for scanning spaces such as the abdomen which include relatively few obstructions.

Abstract: The coagulation of blood is measured by introducing the blood into an annular gap in a beaker formed between the inner surface of the beaker and a cylindrical member depending into the beaker. The beaker is mounted on the upper end of a rod-like support. A coil arrangement about the lower part of the rod-like support impresses a circular orbiting motion on the support and beaker. Another core associated with the rod-like support measures changes in amplitude of the support produced by the development of fibrin in the blood sample in the annular gap.

Abstract: A fluid, for example, blood, specimen holder for biological testing comprises an elongate transparent tube of equilateral triangle cross section. The intersection region of two sides of the tube forms a channel for controlling, channelling, and concentrating flow of a fluid specimen as the tube is agitated to flow the fluid specimen back and forth between ends of the tube during biological fluid testing. The third side of the tube opposite the fluid flow channel provides a flat impinging surface for a light source used in determining translucency characteristics. A removable end cap for the tube is formed having a small diameter inner portion which projects into the tube when the cap is installed thereon. A transverse diaphragm provided at the inner end of the inner portion enables the cap to be penetrated by a hypodermic needle for introducing a fluid specimen into the tube. The projecting inner portion is configured for preventing escape of fluid from the tube during biological testing.

Abstract: Device for volumetric testing of pressure-vessel walls and pipes with a combined transmit-receive test head for scanning a test track having a given test-track spacing, includes an oscillator unit including an oscillating crystal and a receive oscillating crystal having respective centers spaced apart a distance smaller than that of the test-track spacing so that the test head has a full width within which at least one additional oscillating crystal is accommodated, the additional oscillating crystal being paired with one of the transmit and receive oscillating crystals so as to form therewith another oscillator unit including a transmit oscillating crystal and a receive oscillating crystal having centers spaced apart a distance smaller than that of the test-track spacing, the distance between the crystals of both of the oscillator units being substantially equal.

Abstract: A clot lysing timing device consisting of a thermostatically controlled assembly including heated blocks formed with wells to receive precooled test tubes containing liquid with clots formed by the addition of thrombin to plasma (or to a mixture of fibrinogen and plasminogen) containing varying quantities of urokinase, streptokinase or plasmin. The blocks are maintained at 37.degree. C. when a precooled test tube with such contents is placed in one of the 37.degree. C. wells it activates a microswitch which starts a corresponding timer channel. An opaque sphere is placed on top of the clot. As the clot dissolves (at a rate depending on the quantity of lytic agent incorporated in the clot) the sphere travels to the bottom of the test tube, interrupting an infra red light beam, which stops the corresponding timer channel. The time counts from the respective timer channels can be selectively displayed on an LED digital readout device.

Abstract: A method and apparatus for determining the gel strength of drilling mud by the repetitive steps of: flowing mud through a conduit positioned in a nonhorizontal attitude at a flow rate where the shear rate of the mud is in the range of greater than zero to about 20 sec..sup.-1, interrupting the flow of mud to provide a static column of mud in the conduit, and measuring the differential pressure of the mud between vertically spaced points during both the flow and static intervals.

Abstract: A method of and apparatus for determining the gel point of a sample of epoxy resin. An aluminum foil tube containing the sample is inserted into the test pressure sensor which is located within a preheated laboratory environmental chamber. The test pressure sensor consists of two knurled cylinders each rotatably mounted about its axis wherein the axes are parallel and the plane of the two axes is horizontal. The axis of one of the cylinders is fixedly mounted. The axis of the other cylinder is slidably mounted within the horizontal plane of the two axes. A spring tends to force the axis of the slidably mounted cylinder toward the axis of the fixedly mounted cylinder. The sample becomes liquid within the tube, and the two are drawn into the nip of the cylinders by their rotation. The cylinders continue to rotate collapsing the sample tube within the nip of the cylinders causing the liquid resin to be displaced above the nip of the cylinders within the sample tube.

Abstract: In a rotating probe ultrasonic system the effective PRF may not be sufficiently high for certain purposes, such as examination of the foetal heart. The invention combines fixed transducers looking at a limited region with a rotating probe scanning over a larger region to give a higher effective PRF in the limited region. The two displays are preferably separate although the display of the larger region may conveniently indicate the location of the limited region.

Abstract: A blood bank microscope in which cell/serum-reagent reactions can be viewed, from below, directly in the cuvettes in which the reactions take place and in which the cuvettes can be rocked to cause the contents thereof to flow back and forth within the viewer's field of observation.

Abstract: The coagulation of blood is measured by introducing the blood into an annular gap in a beaker formed between the inner surface of the beaker and a cylindrical member depending into the beaker. The beaker is mounted on the upper end of a rod-like support. A coil arrangement about the lower part of the rod-like support impresses a circular orbiting motion on the support and beaker. Another core associated with the rod-like support measures changes in amplitude of the support produced by the development of fibrin in the blood sample in the annular gap.

Abstract: A method for the measurement of the aggregation rate of particles suspended in a liquid, particularly of red blood corpuscles in the blood by measuring the intensity of a light beam impinging on the blood sample and leaving the sample again, wherein said blood sample is arranged in a disc cuvette in the horizontal beam path of a light source and is subjected to a shear movement during the course of the measurement of the light beam leaving the sample, and an apparatus for carrying out this measurement.

Abstract: An apparatus capable of determining the clotting time of blood, without requiring continuous inspection of the sample, is disclosed. The apparatus includes a support frame, which is capable of supporting therein a syringe containing a blood sample, and a turntable adapted to rotate at a known rate of speed. Blood from the syringe drops onto the turntable, the clotting time being automatically and graphically depicted by a chart rotatively carried upon the turntable. The apparatus can also be employed for determining variations in the viscosity of blood plasma and other fluids.

Abstract: Apparatus for determining blood elasticity parameters, comprising a cylinder suitable to be immersed in a blood container subjected to regular oscillations. The cylinder is rigidly secured to a frame oscillating according to a vertical axis and mechanically connected to an electromagnetic device generating a reaction force; the frame is also connected to a linear electromagnetic transducer suitable to supply signals to a thromboelastogram recording apparatus.

Abstract: An ultrasonic sector scanner for producing a sector scan in an object to be examined in which one or more ultrasonic transducers are positioned to direct ultrasonic waves toward the surface of one or more movable reflectors. The movable reflectors traverse an arcuate path with respect to a stationary reflector which is positioned to receive the ultrasonic waves scanning the surface of the stationary reflector from each of the movable reflectors and converge such waves at a point in front of the stationary reflector.

Abstract: An object surrounded by media of differing acoustical impedances (e.g., an anatomical organ surrounded by other kinds of tissue within the human body) is acoustically imaged by an array of ultrasonic transducers affixed to the outer surface of an ultrasonic lens. In a preferred embodiment, the lens is homocentric, with the common center of curvature of the inner and outer surfaces of the lens being located at a relatively small acoustic aperture in the body so that object points distributed over a relatively large solid angle from the aperture can be imaged with minimum lens aberations. Where the object to be imaged is a human heart, the acoustic aperture is most conveniently located at an intercostal space between adjacent ribs.

Abstract: A duplex imaging system with a common transducer array for both modes of operation satisfies the conflicting bandwidth requirements by single impulse excitation of the transducer in B-scan imaging operation to generate a wide bandwidth ultrasound pulse and multiple impulse excitation at the emission frequency in Doppler mode operation to generate a narrow bandwidth ultrasound phase. The multiple impulse excitation has a variable repetition frequency depending on range to a sample volume and velocity of blood flow. A Doppler modality, in which the frequency shift of echoes caused by flow of blood is measured to derive the flow velocity, is incorporated into a sector scanner with little additional complexity.

Abstract: A linear transducer array for transmitting and receiving acoustic waves in both pulse-echo and holographic modes of operation. For pulse-echo acoustic imaging the array includes a linear subarray of transmitting transducer elements disposed in a plane along a longitudinal axis. Each transmitting element has an elongate shape and a principal axis that is perpendicular to the longitudinal axis of the array. For holographic imaging the apparatus further includes a removable mechanical shutter for blocking a predetermined portion of the principal axis of each of the transmitting elements so that a dispersive acoustic beam can be generated. The array also includes a linear subarray of receiving transducer elements coplanar with the transmitting subarray and disposed parallel to the longitudinal axis. The subarray of receiving elements is used to detect the reflected acoustic waves for both holographic and pulse-echo imaging.

Abstract: A positionally variable mounting assembly for transducers used to interrogate a nuclear reactor vessel is disclosed. Means are provided for clamping each transducer of an array about its flange in a central restraining block. The central restraining block is, in turn, pivotally mounted in a yoke.The yoke is movable secured to bars or rails bolted to the transducer plate and, by loosening appropriate bolts, can be moved along the ways or pivoted about one of them. Further, the restraining block can be removed from the yoke and pivotally clamped in a different orientation to upstanding brackets attached to the transducer array plate, or rotated through 90.degree. and then secured again in the yoke.

Abstract: A cascade charge coupled delay circuit including a plurality of serial delay line sections formed on a single semiconducter wafer, said delay line sections being directly coupled to one another through the wafer and means for independently clocking each section of said lines.

Abstract: The viscosity of a fluid material, e.g. a synthetic-resin composition, or the coagulation of blood or plasma monitored by placing a quantity of the fluid substance on a support, directing a beam of light upon the sample, detecting reflected light from the sample and vibrating the support at a given frequency and amplitude to disturb its surface. The reflected light detected is a function of the viscosity or the degree of coagulation.

Abstract: A thromboelastographic apparatus comprises a body suspended to a resilient tape and immersed in operation in a liquid to be studied. The liquid is received in a receptacle which is oscillated about the axis of the tape with a predetermined frequency and amplitude. The amount of oscillatory movement impressed to the body is measured by induction.

Abstract: An ultrasonic scanner for producing a sector scan in an object to be examined in which one or more ultrasonic transducers traverse an arcuate path with respect to a reflector which is positioned to receive the ultrasonic waves scanning the surface of the reflector from each of the transducers and converge such waves at a point of a preselected distance in front of the reflector. In general, the ultrasonic waves are converged at a point outside the scanner and inside the object to produce a sector scan in the object having its center at the convergence point. In one embodiment of the scanner the reflector only partially reflects the ultrasonic waves and an additional stationary transducer is provided which is positioned to produce ultrasonic waves which radiate through the reflector and coincide with one of the lines of the sector scan, thus permitting simultaneous M-mode or pulse Doppler echo information to be obtained in perfect registration with the sector scan lines.

Abstract: A search unit for detecting internal flaws in the web of a railroad rail includes a plastic polymer shoe having a base surface contoured to conform generally to the web surface and of sufficient width to extend substantially across the width of the web. A plurality of dual ultrasonic transducers, each transducer including a transmitter and a spaced receiver, form a linear array across the width of the shoe and are angled with respect to each other. A couplant fluid is injected between the shoe and the rail web through fluid inlets in the shoe as the unit is slid along the rail.

Abstract: An ultrasonic transducing unit comprising a central section, which cooperates with only a small portion of the relatively large aperture of an acoustic lens, and an annular section, which cooperates with the remainder of the aperture, can be selectively operated by switch means to utilize the relatively large depth of focus detected signal of the central section alone or to utilize the relatively small depth of focus detected signal of both the central and annular sections together.

Abstract: The transducer is constructed from individual transducer elements arranged in an array and configured to exhibit a predominant, longitudinal mode transversely to the array. The elements are interconnected through thin flexible sheets. Each element is individually damped, and the transducer as a whole is electrically damped through resonance with the clamped capacitance and dissipation. Electrical control permits in-phase operation of all transducer elements or control with preselected phase differences.

Abstract: The apparatus comprises a massive body accurately maintained at 37.degree. and having a through horizontal bore in which are disposed in succession a bulb, a first concentrating lens, a test tube containing the sample, an interchangeable optical filter, a second concentrating lens and a photo-electric cell. The test tube is disposed in a blind vertical bore of the body and it contains a small stirrer bar resting on its bottom and made of a magnetic material. A permanent magnet, adapted to be operatively associated with the stirrer bar is rotated below the body, co-axially to the bar, by an electric motor at one of two accurately controlled speeds. The output of the cell is amplified and applied to one inlet of a differential amplifier the other inlet of which receives the output of a memory wherein the response of the cell has been registered at the beginning of a test. The outlet signal from the differential amplifier starts therefore from zero and may be applied to a usual graphically recording apparatus.

Abstract: A method and apparatus for determining a change of the flow state of a flowable substance by transmitting ultrasonic or ultrasound waves of constant frequency to a spatial region of the substance, receiving ultrasonic waves backscattered by the substance, converting the backscattered ultrasonic waves into a primary signal which is amplitude- and phase-modulated in accordance with the backscattering and demodulating the primary signal in order to obtain a modulation signal. This modulation signal can be divided into a spectrum of signal components of different frequency and possessing pseudo periods which are defined as the time intervals between successive momentary values of the modulation signal, such momentary values corresponding to one another. The time duration corresponding to a predetermined number of pseudo periods is compared with a predetermined time duration.

Abstract: The method consists in generating an electrical signal B which is representative of the time-dependent variations in transparency, in generating a pulse at the initial instant of measurement, in carrying out an initial measurement of the slope of the curve at the beginning of the portion which has a steep slope, in comparing at predetermined instants the measured value of the initial slope with the slope of the curve which is representative of the signal B at these instants, in generating a second pulse when the measured slope becomes significantly different from the initial slope, and in measuring the time interval which elapses between the first and second pulses.

Abstract: Disclosed is a device for determining the activated clotting time of a blood sample, the device being a hand held unit for holding a glass tube containing the blood sample to be tested. The unit includes an electric heater for maintaining the blood sampe at 37.degree. C and an electronic timer. A digital display on the unit can be selectively programmed to display either a temperature or a time function. Upon obtaining the desired temperature, the electronic timer is started and the blood sample is virtually observed in order to determine the elapsed time before the blood sample begins to clot.

Abstract: Moving section plane pictures of a specimen are produced by contacting a predetermined peripheral portion of an ultrasonic transducer head with the specimen in the section plane. The transducer head has a circular internal cavity in which a wheel is mounted eccentrically for rotation about an axis. A plurality of ultrasonic transducers are mounted peripherally on the wheel. The gap formed between a transducer and the internal surface of the transducer head is a minimum along the peripheral portion where contact to the specimen occurs. Each transducer is energized only when passing through the sector subtended by the peripheral portion in contact with the specimen and echoes received by the transducer are displayed on a screen whose base line is synchronized to the movement of the ultrasonic beam.

Abstract: A system for continuously determining the eccentric characteristics of a tube wall, including a positioning assembly supported by the tube when it travels in its lengthwise direction. Two thickness sensors are supported by the positioning assembly and have sensing axes disposed in a predetermined angular relation with respect to one another about the periphery of the tube. The two sensors continuously measure the wall thickness of the tube at the predetermined angular locations as the tube moves in its lengthwise direction. Signal processing circuits are provided for continuously computing the eccentricity characteristics of the tube based entirely upon the comparative values of the thickness readings of the sensors.

Abstract: Combination Doppler and B-scan ultrasonic imaging apparatus is disclosed which includes visual display means for the simultaneous visual display of received ultrasonic Doppler and B-scan information. The apparatus includes first and second focused transducers associated with the Doppler and B-scan systems, which transducers are individually mounted for movement along parallel linear paths. The transducers each comprise a generally semi-cylindrical shaped body of piezoelectric material having opposite end faces upon which electrodes are disposed for connection to Doppler and B-scan transmitter and/or receiver units. The flat side walls of the piezoelectric bodies are positioned closely adjacent a mid-plane extending between the transducers, and means are provided for focusing the transducers at substantially the same depth for operation along a common focal region at, or adjacent, the mid-plane. One such focusing means includes acoustic lenses carried by the piezoelectric bodies.

Abstract: An apparatus for measuring the time taken for a change to occur in the physical state of a material or medium, such as the time of appearance of a clot in a blood sample, includes a jar whose bottom may serve as a circular track for a ball, a ball able to roll around the track, a support for the jar maintaining the bottom of the jar and track in a plane inclined in relation to the horizontal plane, a means for rotating the support and jar whereby the ball remains at the lowest point of the track when the material is in the liquid state but is carried around the track by the more viscous material when that has changed its state, and a means of detecting the movement of the ball.

Abstract: An apparatus and method for accelerating the coagulation of blood and the components thereof uses the injection of an additive and gas to trigger coagulation. The appartus is designed to include a disposable multi-cell pack for minimizing manual handling of the blood and for minimizing exposure thereof to foreign surfaces with each cell containing a specimen of blood disposed above, but separated from, a predetermined amount of additive by means of a releasable cap. The cell pack containing the multiplicity of cells is inserted over a corresponding multiplicity of gas injection nozzles which effect the release of the caps in each cell for injecting the additive and the gas into the blood. As the gas passes through the blood, bubbles that are continually formed in the space above the blood burst and blood transported therein refluxes back into the blood below until coagulation occurs.

Abstract: Short bursts of ultrasonic energy are directed through a three-dimensional specimen to determine the spatial distribution of those structures within the specimen capable of affecting the waveform of the energy. Transducers are placed in spaced positions about the periphery of the specimen to measure the affected parameters (such as attenuation and delay time) of the energy as a result of passing through the specimen along paths between the spaced transducers. The output signals containing this transit time and energy absorption information are retained in a data storage device. Through conventional programming techniques, a computer processes the data and calculates a velocity or absorption profile for each path. The profiles are collectively used to reconstruct two-dimensional or three-dimensional images of the specimen.

Abstract: A method and apparatus for determining coagulation times in such clinical laboratory procedures as prothrombin times tests, activated partial thromboplastin time tests, fibrinogen determinations, factor assays for specific blood coagulation factors, and the like. A fibrous filament is drawn at a predetermined rate through a small body of liquid to be tested and the interval, from the time a suitable coagulating agent is mixed with the liquid to the time the body of liquid clings to the filament and moves with it, is precisely measured as a direct indication of actual coagulation time. The liquid body is supported upon a non-wettable inclined surface bordered by walls defining a well for receiving the liquid and a pathway for its movement. Particularly effective results are achieved by utilizing a pair of spaced filaments moving at precisely the same rate, the filaments being bridged by a web or mass of clotted liquid when coagulation occurs.

Abstract: A circuit and apparatus combination for maintaining a balanced or regulated operational condition in test apparatus that includes mechanical drive and sensor elements as the sensor is exposed to the changing conditions experienced in a test sample or a sampled environment. The circuit automatically drives mechanical elements of the system at a resonant frequency or at other prescribed conditions with voltage changes at an output section of the circuit being indicative of changes in the sample tested or in the sensors environment. Drive elements of the circuit are powered by a drive voltage to cause movement of the sensor and the changing power thus used is evaluated and cancelled out, while a separate input or response voltage that is derived from the resulting movement of the same drive elements is introduced to an Operational Transconductance Amplifier together with an input control current likewise derived from such response voltage.

Abstract: A system for measuring the coagulation time of plasma or whole blood. A solution containing the blood sample is irradiated with pulsed ultrasound, and the back-scattered ultrasound is continuously measured. A predetermined quantity of thrombin is then added to the solution, causing the amplitude of the backscattered ultrasound to fluctuate until coagulation occurs. The elapsed time between the addition of thrombin and the inception of coagulation is the coagulation time, and is an indication of the concentration of fibrinogen in the blood sample.

Abstract: A system for determining the coagulation time of blood and components thereof, the amount of anticoagulant to be injected before and during surgery, and the amount of additive required to neutralize the anticoagulated blood during and after surgery. With collected samples of anticoagulated blood inserted into the system coagulation of the blood is accelerated through the controlled injection of a neutralizing additive by a corresponding injection of regulated gas. Failsafe means determine if gas is being injected into the sample and detection means detect the event of coagulation and indicate the elapsed time for coagulation. Before surgery, an anticoagulant is added to the patient's blood in a quantity necessary to avoid coagulation during surgery. The system responsive to the parameters of the patient's sex, height, and weight and/or pump volume and blood volume determines the amount of anticoagulant to be injected.

Abstract: A method and apparatus for determining the pasting temperature of starch and the like is disclosed wherein a quantity of starch granules are mixed to form a slurry which is heated while a light source is passed through the slurry. Photosensor means detect the light transmittance through the slurry and are connected in circuit to place a visual temperature display means in a hold condition displaying a temperature representative of the pasting temperature of the starch when the light transmittance reaches a predetermined threshold.

Abstract: A system and method is provided which has the general capabilities of measuring the speed of coagulation, congealing or solidification of a fluid sample, and which has particular utility in the measurement of the time required by a sample under test to increase viscosity to a particular level. The system and method to be described is predicated on a viscosity principle, and it includes a movable magnetic member suspended in the fluid sample and which changes position when the sample achieves a predetermined degree of viscosity. The change in position of the aforesaid member is photoelectrically or electromagnetically detected, and the time at which the change occurs, is used in the determination of the time required, for example, for the sample to form a fibrin clot, in a blood or plasma sample or to effect a particular reaction causing solidification or congealing of the sample.

Abstract: A method and apparatus for determining coagulation times in such clinical laboratory procedures as prothrombin time tests, activated partial thromboplastin time tests, fibrinogen determinations, factor assays for specific blood coagulation factors, and the like. A fibrous filament is drawn at a predetermined rate through a small body of liquid to be tested and the interval, from the time a suitable coagulating agent is mixed with the liquid to the time the body of liquid clings to the filament and moves with it, is precisely measured as a direct indication of actual coagulation time. The liquid body is supported upon a non-wettable inclined surface bordered by walls defining a well for receiving the liquid and a pathway for its movement. Particularly effective results are achieved by utilizing a pair of spaced filaments moving at precisely the same rate, the filaments being bridged by a web or mass of clotted liquid when coagulation occurs.

Abstract: An apparatus for time delay acoustic spectrographic analysis of fluid composition uses frequency modulated ultrasonic vibrations which are transmitted through the fluid from a sending transducer to a receiving transducer. By scanning the frequency of the modulated vibrations at a sufficiently high rate, standing waves which give erroneous indications of fluid component concentrations, are eliminated. The frequency of the signal at the sending transducer is compared with that at the receiving transducer and a comparing means whose output is related to the frequency difference of the signal at the receiving transducer from the sending transducer measures the number of times this signal shifts 360.degree. during a scanning period. This measurement is directly related to a property of the fluid being measured. The method and apparatus have particular application in the investigation of coagulation in human blood.