Versatile Density Meter and Refractometer Instrument Combinations from Rudolph Research Analytical.Combined Density – Refractive Index instrumentsMany users need to measure both refractive index and density and feel that a combined system will be a good alternative. The advantages of such a system are many; Since parts are shared the total cost of the system may be less. There may be less operator time needed to load and clean the system. Many laboratories combine the density and refractive index results and use them to calculate a third parameter. Having both results exported into the same file makes the calculations easier.