Abstract: A characterization system for performing optical characterization of a liquid sample in a process plant. The system includes a sample section for holding the liquid sample, an inlet having an inlet valve controlling a flow of the liquid sample into the sample section, an outlet having an outlet valve controlling a flow of the liquid sample out of the sample section, a pressurizer pressurizing the sample section, an agitator agitating the liquid sample inside the sample section when pressurized, a measuring device performing optical characterization of the liquid sample inside the sample section while the liquid sample is pressurized and agitate. The inlet and outlet valves are connected to a line pipe, and the system receives the liquid sample from the line pipe through the inlet valve, characterizes the liquid sample, and returns at least a part of the liquid sample to the line pipe through the outlet valve.