A method and apparatus for determining the caliper and/or the ultrasonic transit time through the thickness direction of a moving web of material using ultrasonic pulses generated by a rotatable wheel ultrasound apparatus. The apparatus includes a first liquid-filled tire and either a second liquid-filled...http://www.google.com/patents/US6308570?utm_source=gb-gplus-sharePatent US6308570 - Method and apparatus for ultrasonic characterization through the thickness direction of a moving web
