Apparatus for and method of measuring suspension flowing in tube fractionator

A process control apparatus for controlling a process measured using a flowing suspension which is configured to cause particles of the flowing suspension to be sorted on the basis of their sizes, wherein the process control apparatus receives process information from a measurement apparatus for measuring suspension flowing in a tube fractionator, the measurement apparatus comprising:

• a radiation source configured to direct wave motion to the flowing suspension, a flow of the flowing suspension causing particles of the flowing suspension to be sorted on the basis of their sizes, the radiation source comprising an optical radiation source configured to direct optical radiation as said wave motion to the flowing suspension, the optical radiation comprising (i) at least one beam that is polarized or (ii) a plurality of beams at least one of which is polarized and at least one separate beam that is non-polarized;
• a measuring arrangement configured to measure first values of a first parameter of the wave motion interacted with the flowing suspension at a first wavelength band of the wave motion;
• the measuring arrangement configured to measure second values of the at least one of following:
• a second parameter of the wave motion interacted with the flowing suspension, and the first parameter of the wave motion interacted with the flowing suspension at a second wavelength band of the wave motion, the measurement of the first values and the second values being synchronized with each other;
• the measuring arrangement is configured to form at least one comparison, each comparison being one of the first values of the wave motion as compared to one of the second values of the wave motion;
• the measuring arrangement is configured to form a distribution, which has at least one of the first values as a function of one of the comparisons, as the process information;
• and
• the process control apparatus is configured to control the process on the basis of the process information.

A method of measuring a flowing suspension, the method comprising:

• directing optical radiation as wave motion to the flowing suspension, the optical radiation comprising (i) at least one beam that is polarized or (ii) a plurality of beams at least one of which is polarized and at least one separate beam that is non-polarized, a flow of the flowing suspension causing particles of the flowing suspension to be sorted on the basis of their sizes;
• measuring first values of a first parameter of the wave motion interacted with the flowing suspension at a first wavelength band of the wave motion;
• measuring second values of the at least one of following:
• a second parameter of the wave motion interacted with the flowing suspension, and the first parameter of the wave motion interacted with the flowing suspension at a second wavelength band of the wave motion, the measurement of the first values and the second values being synchronized with each other;
• forming at least one comparison, each comparison being one of the first values of the wave motion as compared to one of the second values of the wave motion;
• and
• forming a distribution which has at least one of first values as a function of one of the comparisons.