Method and apparatus for ultrasonic characterization through the thickness direction of a moving web

Apparatus for determining a transit time of an ultrasonic pulse through a moving web of thin material, comprising:

• a rotatable wheel having an ultrasonic transducer immersed in a liquid, the wheel having an outer surface for engaging a moving web of thin material whose properties are to be measured;
• a reflector of ultrasound positioned within the wheel and immersed in the liquid to reflect at least a portion of an ultrasonic pulse back to the ultrasonic transducer;
• and
• a circuit associated with the transducer for timing a time of propagation from a time the ultrasonic pulse is emitted by the ultrasonic transducer to a time when the pulse reflected by the reflector is received to provide a transit time of the pulse through the liquid.

Apparatus for determining a transit time of an ultrasonic pulse through a moving web of thin material, comprising:

• a rotatable wheel having an ultrasonic transducer immersed in a liquid, the wheel having an outer surface for engaging a sample whose properties are to be measured;
• a reflector of ultrasound positioned within the wheel and immersed in the liquid to reflect at least a portion of an ultrasonic pulse back to the transducer;
• a circuit associated with the transducer for timing a time of propagation from a time the ultrasonic pulse is emitted by the transducer to a time when the pulse reflected by the reflector is received to provide a transit time of the pulse through the liquid;
• and
• a second wheel filled with liquid and having a second ultrasonic transducer therein, the second ultrasonic transducer receiving at least a portion of the pulse from the second transducer from which a time of flight is determined, the time of flight being indicative of a property of the sample between the wheels.

Apparatus for determining a transit time of an ultrasonic pulse through a moving web of thin material, comprising:

• a rotatable wheel having an ultrasonic transducer immersed in a liquid, the wheel having an outer surface for engaging a sample whose properties are to be measured;
• a reflector of ultrasound positioned within the rotatable wheel and immersed in the liquid to reflect at least
• a portion of an ultrasonic pulse back to the ultrasonic transducer;
• a circuit associated with the ultrasonic transducer for timing a time of propagation from the time the ultrasonic pulse is emitted by the ultrasonic transducer to a time when the pulse reflected by the reflector is received to provide a transit time of the pulse through the liquid;
• and
• a rotatable cylinder that reflects the pulse back to the ultrasonic transducer, a time of flight of the pulse reflected from the rotatable cylinder being indicative of a property of the sample between the wheel and the cylinder.