Abstract: A pressure sensitive device, such as a piezoelectric strip or plurality of piezoelectric crystals, is or are arrayed along the surface of a roll, preferably in a spiral pattern, extending for one revolution of the roll which is nipped with another roll. The nip pressure between the rolls, with or without a paper web passing through the nip, produces a signal by the piezoelectric device indicative of irregularities along the nip. These irregularities, which can be indicative of variations in the web caliper, roll surface, hardness and other parameters of roll or web quality, are then passed to a monitor for continuous read-out of the irregularities or non-uniformities along the face of the roll. Other apparatus, such as a signal conditioner and a signal encoder, can be provided for processing the signals determining the exact axial location along the roll surface of the pressure sensitive device passing through the nip at any given time.