Abstract: An apparatus and method for on-line monitoring of a characteristic of a process liquid stream includes a cell for isolating a precise volume of the liquid. There are provided means for over-filling a sample chamber and means for removing the excess from the chamber comprising a downwardly extending drain line which terminates at a precisely positioned, downwardly facing inlet and means for applying negative pressure to the drain line to draw the excess liquid upwardly from the captured volume until the liquid level reaches the inlet and entry of air disrupts the liquid draining effect. The embodiment shown employs a closed volume, a vent, a conduit for delivery of process liquid into the cell under pressure and a syphon/drain line for removing excess liquid from the cell volume until there remains only a sample of accurately repeatable volume.

Abstract: An apparatus and method for on-line monitoring of a characteristic of a process liquid stream includes a cell for isolating a precise volume of the liquid. A sample chamber is over filled and the excess removed from the chamber by using a downwardly extending drain line which terminates at a precisely positioned, downwardly facing inlet negative pressure is applied to the drain line to draw the excess liquid upwardly from the captured volume until the liquid level reaches the inlet and entry of air disrupts the liquid draining effect. The embodiment shown employs a closed volume, a vent, a conduit for delivery of process liquid into the cell under pressure and a syphon/drain line for removing excess liquid from the cell volume until there remains only a sample of accurately repeatable volume.