What is a Refractometer?

What is a Refractometer?

When many people hear “refractometer”, they think about the device that measures sugar concentration.

Most devices that measure sugar concentration are of this same configuration, wherein light is shined through a prism onto the test sample, and the angle of refracted light changes for each sample.

By measuring the refraction (refraction rate) of light, the refractometer can be used as a measuring device various concentrations.

Measurement Principles of KEM Refractometers

When light passes through highly refractive materials into less refractive materials, its direction changes. When angle of incidence β increases, the output angle a increases according to Snell’s Law, and when output angle a reaches 90 degrees (the critical angle), total refraction occurs on the border surface.

On an actual refractometer, the light source, prism (nD = 1.768), and line sensor CCD are positioned as pictured on the left. The strength of the refracted light is detected by the line sensor CCD, and by finding the border of “light” and “dark” above the line sensor by the CCD address, the refraction rate can be measured.