| 摘要 |
<p>A system that monitors and maintains the concentration of material in a fluid carrier which includes means (22) for circulating the fluid carrier within a substantially closed loop system (12) and means (34) for measuring the concentration of material carried in the fluid. The measuring means includes means (40, 55, 59) 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 transmissivity 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. If a disparity exists between several consecutive samples and the disparity in each case remains below the predetermined value, the samples so observed are determined as valid and representative of continuous depletion of the concentrate material in the fluid carrier. When several of these consecutive and validated sample values of transmissivity exceeds a predetermined threshold and there has been no interruption in such sampling due to a disparity between samples greater than the predetermined value, an enablement will be provided to permit concentrate material to be added to the fluid carrier. The system of this invention has particular application to monitoring the level of toner concentrate in the fluid carrier of a fluid toner development system in an electrographic printer/plotter.</p> |
