A deflection-type refractometer with extended measurement range having a light source generating a beam of light; a measuring cell with a sample chamber receiving a sample liquid; an optical sensor mounted on a movable platform for detecting the deflected beam of light; a driving unit configured to move the platform; a distance measurement unit for monitoring the displacement of the platform; a control unit configured to calculate the deflection of the beam of light based on the displacement of the platform and an output signal of the optical sensor to obtain a refractive index measure of the sample liquid using the calculated deflection.