Abstract: Systems and methods for liquid flow sensing and control for use with a variety of different types of liquid flow measurement and control systems. The liquid flow sensor system senses a flow signal indicative of the flow rate of the liquid flowing in a sensor conduit and analyzes the flow signal to determine, by detecting characteristic changes in the signal, whether a bubble is present in the sensor conduit. Where the system determines that a bubble is present, it may generate an alarm signal indicative of the presence of the bubble. A flow control system incorporating the flow sensor as a feedback source may respond to the detection of a bubble by temporarily freezing the flow control parameters until the bubble has exited the sensor conduit. The flow control system can implement procedures for clearing a bubble from the sensor conduit where the system detects that the bubble has become stuck.

Abstract: An ultrasonic flow meter includes a conduit, a first ultrasonic transducer, a second ultrasonic transducer, and a controller. The first ultrasonic transducer is disposed at a first position about a first portion of the conduit to transmit a first ultrasonic signal and to receive a second ultrasonic signal. The second ultrasonic transducer is disposed at a second position about a second portion of the conduit that is spaced apart from the first position along a length of the conduit to transmit the second ultrasonic signal and to receive the first ultrasonic signal. The controller is configured to cross-correlate the first and second received ultrasonic signals and generate a resulting time-domain signal, analyze the resulting time-domain signal to determine a difference in transit time between the first and second received ultrasonic signals, and calculate a rate of flow of a fluid in the conduit based upon the determined difference.