<P>Refractometers measure the concentration of chemical solutions by measuring their refractive index. Models are available that measure refractive index directly, or have been designed for a specific chemical solution, e.g. salt or sugar.</P><P>The Kern ORA range are universal, maintenance-free analogue manual refractometers. Their practical and robust design means that they can be used simply, efficiently and repeatedly in a production environment. Conversion of the displayed value is avoided by the use of selectable scales, eliminating user error. The scales have been specially developed, precisely calculated and have very thin, clear graduation lines. All models are fitted with an eyepiece that is adjustable to match the individuals' eyesight.</P>