Measuring the speed of ultrasound in a moving web of paper

Abstract

Disclosed are apparatus and methods for producing electrical signals that can be used to measure the speed of ultrasound in a moving web of paper. The apparatus employs a hollow cylinder in which a plurality of transducers are positioned to contact the web. Power supplied to the cylinder through mercury slip is filtered by power conditioning circuitry in the interior of the cylinder, thus enabling the delivery of clean electrical pulses to the emitting transducers. Signals from the receiving transducers are delivered to voltage-to-frequency converter circuitry in the interior of the cylinder, and the resulting electrical frequency signals are converted to optical frequency signals. The optical signals are then communicated across an air gap to receptors which are external to the cylinder. Thus, signals from which measurements of the speed of ultrasound can be derived are provided substantially free from noise generated by transmission through slip rings.

Dependencies are inferred from the claim text.