Abstract: The invention relates to an NMR system, and more particularly to an NMR measurement unit including a flow channel for separating a sample from a fluid stream in a process channel, a magnet arranged relative to flow channel for creating a magnetic field in part of flow channel, a coil arranged relative to flow channel for exciting NMR active nuclei of the sample in flow channel and for receiving the frequency pulse that returns to coil from NMR active nuclei, a frame comprising a fastening flange for sealing NMR measurement unit to process channel and a chamber that is closed relative to fluid stream and connected to fastening flange, arranged to be installed mainly inside process channel, within which chamber magnet and coil are arranged and through which chamber the flow channel passes, the frame installable such that flow channel is positioned inside process channel.

Abstract: Disclosed is a method for determining fibre porosity in a fibre suspension. A sample is taken from a fibre suspension and fibre porosity determination is performed by determining the ratio of fibre-internal water to fibre-external bound water as an online measurement using a NMR spectroscope in successive steps of: generating a magnetic field for exciting protons of water contained in the sample; exciting water molecules of fibre suspension contained in the sample with a frequency pulse provided by a coil; measuring a return signal of the frequency pulse that returns from water molecules to the coil; determining the proton relaxation time and the amplitude of the return signal from the return signal; and determining fibre porosity of the fibre suspension based on the amplitude and the relaxation time of the exponential return signal. Also disclosed is a device for determining fibre porosity of a fibre suspension and a control system connected to a fibre web machine.

Abstract: The invention relates to an NMR system, and more particularly to an NMR measurement unit including a flow channel for separating a sample from a fluid stream in a process channel, a magnet arranged relative to flow channel for creating a magnetic field in part of flow channel, a coil arranged relative to flow channel for exciting NMR active nuclei of the sample in flow channel and for receiving the frequency pulse that returns to coil from NMR active nuclei, a frame comprising a fastening flange for sealing NMR measurement unit to process channel and a chamber that is closed relative to fluid stream and connected to fastening flange, arranged to be installed mainly inside process channel, within which chamber magnet and coil are arranged and through which chamber the flow channel passes, the frame installable such that flow channel is positioned inside process channel.