Abstract: A method and apparatus for monitoring the fiber surface development of pulps due to the refining or beating of mechanical or chemical pulps; an optical cell, fabricated with light-transparent windows, permits an incident collimated beam of light to pass through pulp stock flowing through the cell. The beam is transmitted through a polarizing filter prior to entering the cell, and through a second, crossed, polarizing filter, on exiting from the cell. The exit beam converges onto a photodetector. A gradual variation in the mass of fibers of the pulp stock is established over a predetermined range and this produces a change in the intensity of the transmitted light. As the light intensity changes, it passes through a maximum value; this is accompanied by a similar change in the photodetector electrical output signal.

Abstract: A sensor for the detection of wood chip level in a digester, for example, a Kamyr digester, which consists of: (a) a probe, several meters long, vertically mounted inside the top part of the digester; (b) a series of bare metal electrodes in the side of the probe, spaced typically a few centimeters apart, and electrically insulated from the probe wall; (c) electronic circuit processing to allow any pair of electrodes to be selected, and (c) a means to allow the electrical properties of a liquor or wood chip and liquor mixture between the electrodes of a pair to be measured, and the level deduced from the measurement.