The present invention relates to an apparatus and method for optical measurement of a parameter related to motion of light-scattering particles within a fluid by manipulating analog electrical signals. In some embodiments, first and second analog signals are respectively obtained from first and second photodetectors respectively located at first and second locations. A technique is disclosed for boosting a fraction of an analog electrical signal attributable to light scattering fluctuations and/or to stochastic effects and/or to speckle measurements and/or to DLS measurements. According to this technique, a hybrid analog signal or a difference analog signals is obtained from the first and second analog signals, and is analyzed. Exemplary fluids include but are not limited to biological fluids (e.g. blood plasma). Teachings disclosed herein may be employed in vitro or in vivo.
