METHOD AND APPARATUS FOR MEASURING THE CONTENT OF SUSPENDED SUBSTANCES IN A FLOWING MEDIUM

摘要

Method and apparatus for measuring the content of suspended substances in a flowing medium by illuminating the medium with light from a light source (1). Said light is reflected in at least two detectors (2-4), at least one (2) of which measures directly reflected light and the other (3; 4) measures multiply reflected light. The detector (2) is disposed at a distance from the light source (1) such that a linear relationship between its output signal and the concentration of the flowing medium is obtained. The detector (3; 4) is disposed at a distance from the light source (1) such that its output signal mainly will be constant in relation to the concentration of the flowing medium within a large interval. A measure of the concentration of the flowing medium being independent of disturbing factors such as for example pulp colour is subsequently obtained from the quotient of the signal provided by direct reflection divided by the signal provided by multiple reflection.