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 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: 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: 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 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.