Turbidimeter utilizing back scatter

Claim 1

A turbidimeter comprising: a fluid line with a single opening and a wall opposite said single opening, probe means mounted in said single opening for sensing the turbidity of the fluid flowing in the line comprising face means providing a surface contacting said flowing fluid, light source means for providing a source of incident collimating light, first light transmission tube means communicating said source of incident light with said face means so that incident light passes along an axis through said face means into the line substantially perpendicularly to said wall, and photosensitive means for sensing the back scatter light from the incident light received by said photosensitive means, second light transmission tube means communicating said photosensitive means with said face means so that said back scatter light is received along an axis passing through said face means which is substantially parallel to and axially offset from said axis of said incident light, a lens for focusing said back scatter light on said photosensitive means, said photosensitive means for providing an electrical characteristic varying in magnitude in accordance with the variations in the magnitude of the intensity of the back scatter light and instrument means responsive to the variation in the electrical characteristic for providing an indication of the turbidity of the fluid in the line, said source of incident collimated light passing through said face means substantially perpendicularly with respect to said wall providing minimal divergence of light reflected from said wall to said photosensitive means to minimize the quiescent level of light received by the photocell.