Patent ID: 8091407

Claim:
A method of monitoring a flowing medium for the presence of air, comprising: coupling of a sequence of ultrasonic signals of at least one preset amplitude into the flowing medium; receiving the ultrasonic signals emerging from the flowing medium over a time interval; for each ultrasonic signal: comparing the amplitude, or a parameter which correlates with amplitude, of the ultrasonic signal with a preset reference level; determining that a given volume of air is present in the flowing medium if the amplitude of the ultrasonic signal is below the preset reference level; determining that the given volume of air is not present in the flowing medium if the amplitude of the ultrasonic signal is equal to or above the preset reference level; determining the flow-rate of the flowing liquid and creating a limiting value (N) as a function of the flow-rate; determining a number of successive time intervals (n) in which the amplitude of the ultrasonic signal is below the preset reference level; comparing the number of successive time intervals (n) with the limiting value (N); concluding that there is a first incident if the number of successive time intervals (n) is above the limiting value (N), wherein the first incident is a large air bubble; determining a number of events (p) in which the number of successive time intervals (n) is equal to or below the limiting value (N); comparing the number of events (p) with a preset reference value (P); concluding that there is a second incident if the number of events (p) is above the preset reference value (P), wherein the second incident is a plurality of small air bubbles; generating a first alarm signal, a first control signal, or both a first alarm signal and a first control signal when the first incident is detected; and generating a second alarm signal, a second control signal, or both a second alarm signal and a second control signal, when the second incident is detected.