Abstract: A method and apparatus for occlusion monitoring in a flow circuit using pressure waveform analysis. The flow circuit includes a first conduit and a second conduit which fluidly interconnects a fluid supply with the first conduit. A pump is disposed in an intermediate portion of the second conduit. Monitoring of the pressure in the first conduit is used to identify any occlusions in that portion of the second conduit which is disposed between the pump and the fluid supply.

Abstract: A method for correcting the effect of transducer temperature variations in an ultrasonic flowmeter. The method includes the steps of providing ultrasonic transducers having resonant frequencies that are approximately linear functions of temperature, and applying to those transducers bursts of ultrasonic drive pulses having a frequency that is independent of temperature. The method further includes the steps of calibrating said apparatus at a temperature approximately equal to the nominal temperature if said transducers, and using sample measurements taken at an unknown temperature to define a linear representation of how sample measurements vary during the course of bursts. Finally, the method includes the step of using the linear representation to correct fluid flow values calculated from the sample measurements.

Abstract: An ultrasonic flowmeter for measuring the rate of flow of a fluid by means of bursts of ultrasonic drive pulses that are alternately transmitted and received by first and second ultrasonic transducers. A driver circuit is suitably coupled to the first and second transducers to cause the latter to alternately transmit ultrasonic signals in first and second directions through the fluid to be measured. A receiver circuit is coupled to the first and second transducers to cause the latter to alternately receive ultrasonic signals in first and second directions through the fluid to be measured. First and second driver switching means, preferably including tri-state buffers, allow the same driver circuit to drive both transducers. The driver and receiver circuits are directly coupled to the transducers and share a common ground.

Abstract: An ultrasonic flowmeter for bidirectionally measuring the rate of flow of a fluid. Two spatially separated ultrasonic transducers alternately transmit and receive bursts of ultrasonic drive pulses through a fluid to be measured. A reference signal generator generates, for said bursts of drive pulses, reference transitions which occur controllable times after the beginnings of the bursts. A sampling signal generator generates sampling signals that define a plurality of sampling windows for use in timing the transitions of the received signal. The timing of the reference transition is dynamically adjusted so that the transitions of the received signal remain within respective sampling windows.

Abstract: In a fluid flow measuring apparatus, a flow of fluid is established through the apparatus at a first known flow rate. For each of two states of the apparatus, electrical drive pulses are applied to transmitting transducers. From the output signals of receiving transducers upcount and downcount values are derived which are indicative of the elapsed times between the drive pulses applied to the transmitting transducers and the zero crossings of the output signals of the receiving transducers, with the values being stored in a form that indicates the frequency of occurrence thereof. At least one test is applied to the stored upcount and downcount values to determine if the values have an acceptable distribution and if so using the stored values to determine a first calibration value for the apparatus. Then a flow of fluid is established through the apparatus at a second known flow rate. Again, for each of two states of the apparatus, electrical drive pulses are applied to transmitting transducers.