NMR measurement unit fixable within a process channel

An NMR measurement unit comprising

• a flow channel comprising a first end and a second end for separating a sample from a fluid stream present in a process channel via the first end and for returning the sample to the fluid stream via the second end;
• a magnet arranged in connection with the flow channel for creating a magnetic field at least in part of the flow channel;
• a coil arranged in connection with the flow channel for exciting an NMR active nuclei of the sample moving in the flow channel and for receiving a frequency pulse that returns to the coil from the NMR active nuclei;
• a frame being installable in such a way that the flow channel is positioned inside the process channel, the frame comprising a fastening flange for sealing and fastening the NMR measurement unit to an inspection hatch or a service opening in a wall of the process channel, and the NMR measurement unit is adapted to be installed in the inspection hatch or the service opening, respectively, of the wall of the process channel by means of the fastening flange;
• a chamber connected to the fastening flange and arranged to be installed at least mainly inside the process channel, said chamber is closed at least relative to the fluid stream, and within said chamber the magnet and the coil are arranged, and through said chamber the flow channel passes, and wherein both the magnet and the coil encircle the flow channel.