Principle Operation of a "Critical Angle" Inline Refractometer

Refractometer principle operation, How refraktometer works

     The LSC Process Refractometer utilizes the "critical angle" technique - an interface measurement of refractive index. The critical angle is defined as; that specific angle of incidence where a light ray traveling through the sensing window either breaks through the interface (wetted surface) or reflects from that surface like it were a mirror.  This is a function of the optical density of the sensing window (Prism) and the optical density (refractive index) of the process fluid being measured.


Our design employs the "I.R. Detection System" that provides Infinite Resolution while eliminating drift.  In simple terms: At the prism face, light is reflected and refracted off the process, at different angles, depending on the refractive index level (optical density) of the process fluid. This technique measures the total amount of "dissolved solids" of the process stream.


Process conditions such as entrained air, viscosity, suspended particles or crystals, color (whether opaque or transparent), will not interfere with the accuracy of the concentration measurement.

To learn more about process refractometers see:

.How do refractometers work? How does a refractometer work?