Ultrasonic air flow sensor

A flow sensor, comprising:

• a duct having an inner surface and an outer surface, the inner surface defining a flow passage through which fluid may flow in a flow direction;
• a plurality of first ultrasonic transceivers coupled to a first portion of the outer surface of the duct, each of the first ultrasonic transceivers configured to (i) transmit ultrasonic waves into the fluid, (ii) receive ultrasonic waves, and (iii) supply sensor signals representative of the received ultrasonic waves;
• a plurality of second ultrasonic transceivers disposed upstream of the first ultrasonic transceivers, each of the second ultrasonic transceivers configured to (i) transmit ultrasonic waves into the air, (ii) receive ultrasonic waves, and (iii) supply second sensor signals representative of the received ultrasonic waves;
• and
• signal processing circuitry in operable communication with each of the first and second ultrasonic transceivers, the signal processing circuitry configured to:
• supply separate excitation signals to each of the first and second ultrasonic transceivers,
• receive the first and second sensor signals supplied by each of the first and second ultrasonic transceivers, respectively, and
• generate, in response to the sensor signals, a flow signal representative of fluid flow in the flow passage,
• wherein each of the first and second excitation signals has a different phase, such that the ultrasonic waves transmitted by each of the first and second ultrasonic transceivers at least selectively combine to propagate in an adjustable direction relative to the flow direction.

A flow sensor, comprising:

• a duct having an inner surface and an outer surface, the inner surface defining a flow passage through which fluid may flow in a flow direction;
• a plurality of ultrasonic transceivers coupled to a portion of the outer surface of the duct, each of the ultrasonic transceivers configured to (i) transmit ultrasonic waves into the fluid, (ii) receive ultrasonic waves, and (iii) supply sensor signals representative of the received ultrasonic waves;
• and
• signal processing circuitry in operable communication with each of the ultrasonic transceivers, the signal processing circuitry configured to:
• supply separate excitation signals to each of the ultrasonic transceivers,
• receive the sensor signals supplied by each of the ultrasonic transceivers, and
• generate, in response to the sensor signals, a flow signal representative of fluid flow in the flow passage,
• wherein each of the excitation signals has a different phase, such that the ultrasonic waves transmitted by each of the ultrasonic transceivers at least selectively combine to propagate in a direction that is perpendicular to the flow direction selectively combine to propagate in a direction that is non-perpendicular to the flow direction.