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Abstract

A system for determining the level of particulate contaminants in a fluid utilizes a porous filtration element having filtration pores therethrough in fluid series with a volume indicator. Preferably, the filtration medium is provided with filtration pores which have a generally predetermined size such that oversized particles of the particulate contaminants are accumulated on one side of the filter medium. In one embodiment, filtration of the fluid continues until the filtration medium is blocked entirely, and then a reading of the volume of fluid which has flowed therethrough is taken. The fluid thus accumulated can be forced back through the filter medium in a backflush direction such that the accumulated particulate contaminants are washed away, thereby rendering the filtration medium ready for a subsequent measurement. In automatic embodiments of the invention, a bistable valve may be utilized, the flow states of the valve being switched to shift from the filtration phase to the backflush phase. A pressure comparison arrangement obviates the need for clogging the filtration medium completely during each measurement phase. This is achieved by issuing a signal when the flow through the filtration medium is reduced to a predetermined level.

First Claim