The turbidity meter is a highly accurate device with a fully submersible sensor for in-situ environmental or process monitoring. It measures solids, turbidity, concentration, consistency and optical density. For turbidity measurement the sensor is a 90 degree scatter nephelometer where a focused beam is directed into the monitored water. The light beam reflects off particles in the water, and the resultant light intensity is measured by a photodetector positioned at 90 degrees to the light beam. The detected light intensity is directly proportional to the turbidity of the water. The sensor utilizes a second light detector to correct for light intensity variations, color changes, and minor lens fouling.