Method and apparatus for obtaining information about the size distribution of macroscopic particles in a liquid

An apparatus for measuring parameters which describe a particle size distribution of particles in a liquid, which apparatus comprises:

• a liquid channel;
• an ultrasonic transducer assembly for generating an ultrasonic beam in the liquid channel containing the liquid;
• a detector for measuring a property of a reflection of the beam by a particle in the liquid in the liquid channel to provide a signal corresponding to a measured value;
• a processing unit arranged for performing a maximum likelihood estimation of the parameters, in view of a combination of a series of the measured values, based on an expression for a probability of the measured values as a function of the measured values, which expression contains a first factor for a probability of a particle reflection measurement of which a particle reflection with the measured value forms part, corrected with a second factor for a probability that there is not also a reflection by a particle in the liquid with a dominating value of the property, which would mask the measured value, forming part of the particle reflection measurement.