A sensor, sensor disk, sensor measurement correction system, and method used in measuring a parameter in the refining zone. The sensor includes a spacer that spaces its sensing element from the disk. In one preferred embodiment, the spacer is made of an insulating material that insulates the sensing element from the thermal mass of the disk to prevent the thermal mass from affecting sensor measurement. The sensor includes a housing carried by the spacer that, in turn, carries the sensing element. Where the sensing element is a temperature sensing element, the housing is thermally conductive and the housing and spacer enclose the sensing element. Each sensor is disposed in the refining surface, preferably in its own separate bore in the disk and flush with or below axial refiner bar height. Signals from one or more sensors are processed by a processing device linked to a module containing calibration data that is applied to make sensor measurements more accurate. The module holds calibration data from sensors that are precalibrated before the sensor disk in which they are assembled is shipped, along with the module, to a fiber processing plant where the disk is installed in a refiner and the module connected to the processing device. In one preferred embodiment the sensor or sensors are carried by a sensor module that can be a removable segment of a refiner disk.

A double disk refiner and inducer for the same that mixes fiber in low consistency (6% or less by weight) stock and urges it towards both pairs of refiner disks of the double disk refiner. In a preferred embodiment, the inducer comprises an impeller that has at least one flight extending radially outward from an inner hub. Each flight is angled and also can be curved so as to substantially continuously mix and urge stock toward the disks. In one preferred embodiment, the inducer is an impeller that has two helical flights that are axially spaced from one another but that overlap in an axial direction. In a preferred method, the low consistency stock is urged by the inducer toward the disks preventing clumping of fibers in the stock and breaking up any clumps already present in the stock. As a result, the gap between the disks can be increased from between one thousand and three thousandths of an inch to increase the output of the refiner.