Measurement Principle - Mettler Toledo RA-510M Bedienungsanleitung

Refractive index
3.2

Measurement principle

Setup of the measurement system
The light source is a light emitting diode (LED) whose beam passes through a polarizing
filter, an interference filter (589.3 nm) and various lenses before it passes through the
sapphire prism and encounters the sample. The reflected light (angle > critical angle) is led
via a lens to the optical sensor, which records the critical angle.
The temperature at the boundary region prism-sample is measured by an embedded sensor
and controlled via a Peltier semiconductor.
6
The light emitted by the RA-510M
passes through the prism and en-
counters the solution. It is partially
refracted (angle of incidence < critical
angle) and partially reflected (angle of
incidence > critical angle).
The reflected light is recorded using
an optical sensor (CCD). The bound-
ary between the dark and light areas
represents the critical angle needed
to calculate the refractive index.
METTLER TOLEDO
RA-510M