Described are devices, methods, and systems that are suitable for rapidly and simultaneously determining the concentration of suspended particles in a sample. The devices, methods, and systems allow for the rapid and simultaneous interrogation of a large number of sample wells in a single vessel, for example, samples contained in a two-dimensional array or micro-titer plate, without the need for moving reading heads or moving the sample vessel. The nephelometry system allows the user to rapidly and simultaneously measure the concentration of the particles in numerous samples, adjust the concentration of the particles in the sample with a sample handling system, and re-measure the concentration of the samples in order to achieve a desired concentration.