Robert S Downing

US Patent:

46601520, Apr 21, 1987

Filed:

Jun 18, 1984

Appl. No.:

6/621965

Inventors:

Robert A. Downing - San Jose CA
Lorin K. Hansen - Fremont CA

Assignee:

Xerox Corporation - Stamford CT

International Classification:

G06G 757
G03G 1500
B67D 508

US Classification:

364509

Abstract:

A system is disclosed that monitors the concentration of material in a fluid carrier which includes means for circulating the fluid carrier within a substantially closed loop system and means for measuring the concentration of material carried in the fluid. The measuring means includes means to detect rapid changes in transmissivity of the fluid carrier, which are indicative of the presence of entrained air bubbles in the fluid carrier, so that measurements of material concentrate under such conditions may be ignored or rejected. Further, to ensure that an accurate measurement of concentrated material depletion is being observed, more than one consecutive measurement is made and validated before concentrate is finally added to the fluid carrier in the system. In the preferred embodiment, the determination of whether air bubbles may be entrained in the fluid carrier is accomplished by determining a disparity between two consecutively measured samples to have been greater than a predetermined value. If such a disparity exists, the measurement sampling rate is increased until the disparity between consecutively measured samples is again less than the predetermined value, at which time sampling is again performed at slower sampling rate.