Clinical Refractometer - Urine SpecificRefractometer Clinical Refractometer measures urine specific gravity, or gives the refractive index in seconds. Dimensions Place a drop or two of a sample on the prism and read the results. Sper Scientific portable refractometers work in ambient light with no battery or other power source necessary. A refractometer measures the extent to which light is bent (refracted) through a liquid sample. They are commonly used to help identify or confirm the