The USEPA-COMPLIANT 2100N Laboratory Turbidimeter from Hach Lange is designed to measure turbidity in either ratio or non-ratio mode.
Light from a tungsten-filament lamp is focused and passed through the sample. The 90-degree scatter detector receives light scattered by particles. Transmitted and forward scatter detectors receive light that passes through the sample.
Ratio and no-ratio turbidity measurement modes are selected using the ratio key located on the instrument keyboard. With ratio toggled off, turbidity is measured using only the single 90-degree detector.
Benefits of the ratio mode include long-term calibration stability, wide measurement range with excellent linearity, and the ability to measure turbidity in the presence of colour.