Liquid, such as milk, enters the sealed container from an inlet at the top of the container and exits through an outlet at the bottom of the container. The quantity of liquid in the container is sensed and a microprocessor calculates the total volume of liquid. During periods of low flow, such as at the beginning and at the end of the milking cycle, the outlet is automatically closed, partially or completely, by a motorized valve connected to the microprocessor, or by a weighted float situated within the container, so as to accumulate the liquid during those periods thereby enhancing the accuracy of the measurement.