Method and apparatus for measuring the degree of contamination of liquids

Claim 1

Apparatus for measuring the degree of contamination of liquids comprising a filter having a container for accommodating a definite volume of a liquid containing contaminants and a stack of a plurality of sheets of filter paper contained in said container, the pore size of said sheets of filter paper decreasing from the first to succeeding sheets in the direction in which the liquid passes therethrough; and a measuring device having a source of light having a definite wavelength and directed against the first and succeeding sheets of filter paper respectively having contaminants with different particle sizes thereon and which have been removed from said filter for irradiating said sheets, photoelectric converting elements positioned to receive light reflected from said sheets of filter paper and responsive to the light reflected by said first and succeeding sheets of filter paper respectively for producing electric signals proportional to the quantities of the contaminants deposited on said first and succeeding sheets of filter paper respectively, and a bridge circuit connected to said converting elements for comparing said electric signals with each other and producing a differential output signal corresponding to the concentration and the particle size of said contaminants.