Abstract: Apparatus and method for non-invasively determining the level of a constituent of a patient's blood drawn though an elastomeric tubing to a dialysis machine deforms the tubing in the slot of a measuring head having two points of different transverse length with a transmit/receive sensor at each point that transmits a signal through the tubing and the blood and is reflected back to it from the tubing internal wall. The round trip transit time of the signal at each sensor is measured and the blood sound velocity is calculated from the two round trip transit times and the differential of the transverse lengths at the two points. Blood hematocrit level, which is related to blood volume, is calculated from the calculated sound velocity and an empirical relationship.

Abstract: A measuring head has a base and extending spaced apart vertical sidewalls that form a slot into which a tube through which a fluid flows is placed and at least one sensor element mounted in at least one of the sidewalls to detect a characteristic of the flowing fluid. At least one through passage is formed in each of the sidewalls that are aligned opposing each other to form a pair of passages through which a strap is passed above the tube in the head slot and a fastener holds the strap bound to the sidewalls to retain the tube in the slot. One embodiment has a pair of the sidewall slots on each side of a sensor element mounted in a sidewall. A passage also can be provided in the head base through which a strap can pass and then be passed through a pair of the sidewall passages.

Abstract: An ultrasonic sensor for measuring the level of liquid in a vessel has an elongated tubular probe, a tube within the probe, and a transducer that converts electrical energy to ultrasonic energy mounted at or near one end of the tube so as to transmit ultrasonic energy horizontally across the probe. An element having a surface that reflects ultrasonic energy is at an angle, preferably of about 45°, to the probe longitudinal axis opposite to an ultrasonic energy emitting part of the transducer to reflect ultrasonic energy received from the transducer upwardly in the probe to an air-liquid interface from which it is downwardly reflected to the angled reflector element that directs the energy reflected from the interface back to the transducer for conversion to an electrical signal that is used by an electronic module to measure the liquid level in the probe which is the liquid level in the vessel.

Abstract: A system and method for measuring the flow rate of a liquid in a tube non-invasively has a heating element that generates energy that is applied to the liquid to produce a heat marker that is detected by a temperature sensor located at a known distance from the heating element and the flow rate is calculated from measuring the travel time of the heat marker from the heating element to the sensor. A second temperature sensor measures the ambient temperature of the liquid before the heat marker is produced and detection of the heat marker is made on the basis of the difference between the ambient temperatures and the temperature of the heat marker.

Abstract: A non-invasive dry coupled disposable/reusable ultrasonic sensor has a housing and a piezoelectric element at one end of the housing to which connected signal leads are connected that extend out from the housing. A piece of double-sided adhesive tape has one adhesive side secured directly to the face at the one end of the housing with the other adhesive side to be secured directly to the outer surface of a pipe or vessel. The tape can cover the entire face of the one end of the housing or only that part that the piezoelectric element faces.

Abstract: Apparatus for measuring the level of liquid in a container has a substrate on which a plurality of piezoelectric elements are mounted that are to transmit ultrasonic energy upwardly through the bottom of a container placed on and supported by the substrate into the container and to receive ultrasonic energy reflected back from the liquid/air interface within the container from which the round trip time can be measured and the liquid level calculated. The plurality of piezoelectric elements are of predetermined shapes and mounted spaced apart on the substrate in an array to accommodate containers with different shape bottoms.

Abstract: A system using ultrasonic energy for detecting and quantifying air bubbles and/or particles in a liquid flowing in a tube by a non-invasive and non-destructive technique has an ultrasonic sensor having piezoelectric transmitter and receiver elements placed opposing on the outside of the tube wall and energy in the ultrasonic frequency range is transmitted from the transmitter element to the receiver element. The received ultrasonic energy is amplified and detected and preferably split into a steady state (DC) component and a varying or transient (AC) component respectively indicative of the absence and the presence of an air bubble or a particle in the liquid. The two components of the signal are applied to an A/D converter whose output is supplied to a microprocessor which uses the digital data that corresponds to the presence of the varying transient component to indicate the presence of an air bubble and/or a particle and to measure its characteristics.

Abstract: An integrated multi-function sensor system has a head having a slot to accept a tube of a deformable material and a plurality of sensor elements mounted in the walls of the head slot to confront a tube in the slot, each sensor element being for affecting sensing of a condition relating to a liquid in the tube. An integrated electronic circuit including a microprocessor operates to determine the various conditions of a liquid flowing in the tube sensed by the sensor elements, which conditions include detection of air bubbles and/or particles by ultrasonic sensing elements, detection of an occlusion in the liquid flow by sensing the deformation of the tube wall by a force sensing element, determining the temperature of the liquid by an infrared temperature sensing element, and determining the color of the liquid by optical elements.

Abstract: A system for determining pressure change in a liquid flowing in a tube of an elastic material has a sensor head having a slot and a pair of piezoelectric elements mounted in opposing walls of said slot between which the tube is placed in contact with the opposing elements. An electronic circuit generates periodic bursts of electro-mechanical energy from one of the elements that is transmitted through the tube to be received by the other element to be converted to an electrical signal from which is measured the travel time value of the energy through the tube and liquid therein and the amplitude value of the received signal which values are compared to at least one of base line travel time and amplitude values to determine a change of pressure of the liquid flowing in the tube.

Abstract: An ultrasonic liquid level sensor instrument that combines a continuous transmitter that transmits though the air for measuring the level of liquid in a vessel on a continuous basis and a point level sensor that sets a high level alarm. The continuous level transmitter/receiver provides a continuous measurement of the liquid level in the vessel and the point level sensor is used for sensing an overflow, or high level condition in the vessel, as well as failure of the continuous transmitter/receiver. The instrument includes a sensor fixture that holds both the continuous air transmitter/receiver transducer and the point level sensor. The fixture is mounted in a single hole in the wall of a tank or a vessel in which the liquid level is being monitored. Each of the continuous level transmitter/receiver and point level sections of the instrument has a self check capability.

Abstract: An ultrasonic transducer for sensing liquid within an article, such as a vassel or pipe, without contacting the liquid has a body, a sealed capsule of a flexible material containing a liquid capable of transmitting ultrasonic energy carried by the body from which a head portion of the capsule extends to contact a wall of the article. Within the body is a piezo-electric element in contact with a portion of the sealed capsule to transmit ultrasonic energy to and receive energy from the liquid in said capsule as it passes through the capsule head without the need for a coupling compound.

Abstract: A non-invasive system and method for measuring liquid level in a vessel utilizes a pair of ultrasonic transducers mounted spaced apart externally on the vessel wall. One of the transducers excites a single pulse of sonic energy that produces a flexural, or elastic, wave in the wall and the second transducer receives the flexural wave to produce an electrical signal waveform corresponding to the travel time of the flexural wave between the two transducers. The electrical waveform signals produced at different times are compared to determine if a phase delay exists between two waveform signals, which indicates that there has been a change in the liquid level condition in the vessel interior space between the two transducers. Measuring the phase delay, or time delay, between the flexural wave components produced at two different times is used to indicate presence or absence of the liquid at a point on the vessel and/or the height of the liquid in the space.

Abstract: A non-contact ultrasonic system for measuring the volume of liquid in a container in which an ultrasonic sensor is disposed opposite the top of the container. A circuit provides pulses of ultrasonic energy for transmission through the air to the air-liquid interface of liquid in the container and for measuring the round trip transit time from the sensor to the interface and back to the sensor. A computer is programmed with dimensional data of the container internal volume and computes the volume of liquid in the container based on the dimensional data and the round trip transit time. The computed volume data is stored. The system can measure the volume of a plurality of containers using a plurality of sensors that are operated in sequence or at the same time or single sensor in which the plurality of sensors are moved relative to the single sensor for the volume of each of the sensors to be sequentially measured.

Abstract: An ultrasonic sensor having a support structure of first and second walls with a gap of fixed distance therebetween. A piezoelectric element for transmitting and receiving ultrasonic energy is bonded to the inner face of one of the walls and the energy transmitted across the gap is reflected from the other wall back to the element. Two timing windows are set, one for the time of energy transmission across the gap with liquid present and the other with the gap being dry. The received energy at the time of the window indicating the dry gap condition is used as a self-test signal to check element dis-bonding. In a sensor with two elements, one bonded to each of the support walls, one element serves as the transmitter and the other as the receiver.

Abstract: A system for counting the number of objects of known thickness in a stack and identifying the objects by their color in which an ultrasonic sensor is mounted at a known distance from a reference point that defines the beginning of the stack. The ultrasonic sensor is operated to measure the round trip transit time of ultrasonic energy reflected back from the closest object in the stack and the number of objects in the stack is calculated on the basis of the known distance and the round trip transit time. A color sensor senses the color of at least one object in the stack to identify the object. In a casino application where the objects are chips of known monetary value, the value of the chips in the stack can be calculated.

Abstract: An ultrasonic sensor for detecting the presence of a liquid having an elongated body of plastic material with spaced arms at one end defining an air gap between the arms with each arm having a piezoelectric element at its inner face. The body houses a circuit board on which components of an ultrasonic sensing circuit that reacts to produce a signal when liquid is present in the air gap. The body is small in dimensions and is flat making it easy to install into restricted space applications.

Abstract: An ultrasonic sensor of either the invasive or non-invasive type having a piezoelectric element for transmitting and receiving ultrasonic energy bonded by an adhesive to the inner face of the wall of a support. When operated in an energy transmitting mode, the energy transmitted by the element is reflected from the interface of the outer face of the wall medium confronting it back to the element. The distance from the front face of the element through the bonding adhesive to the interface is known and when the sensor is in a receiving mode the time of arrival of the reflected signal can be predicted. The received energy is used as a self-test signal to check element dis-bonding. In one embodiment sensor integrity is checked by a digital signal processing technique with the received signal reflected from the interface being periodically sampled and converted into a series of digital numbers.

Abstract: A sensor for determining both the presence of a liquid in a container or conduit, and identifying its type has a sensor housing body containing both a pair of piezoelectric elements used as the transmitter and receiver of ultrasonic waves directed across a gap therebetween in an ultrasonic liquid presence detecting circuit and a pair of electrodes exposed to any of such liquid in the gap used in a circuit for identifying the liquid type. The liquid identification circuit is either of the capacitance type, which produces a variable amplitude output signal depending on the type of liquid in the gap between the two electrodes, or operates to measure the difference in response time between pulses applied to each of the electrodes with one serving as a reference.