The invention relates to a device for particle sizing of particles distributed in a fluid within a household appliance, comprising at least one first emission means emitting a first electromagnetic radiation along a first optical axis into the fluid present in a test volume, at least one first measuring means detecting at least one characteristic of a second electromagnetic radiation emerging from the fluid an evaluation means provided and adapted to evaluate the characteristics of the second electromagnetic radiation, whereby particle sizes can be detected using reference characteristics, wherein the emitted first electromagnetic radiation is quasi-monochromatic or is a sequence of predetermined wavelengths within a predetermined time interval, the first measuring means being arranged off the first optical axis