A measuring device for analyses of particles (2;18;23)comprises - a first feeding chute and a consecutive second feeding chute, - the first feeding chute and the consecutive second feeding chute are arranged so that the first feeding chute is arranged above the consecutive second feeding chute, so that the particles of a flow of particles that falls from a free open end of the first feeding chute are controlled in order for said particles to be delivered in free fall onto the consecutive second feeding chute, - the feed rate of the feeding chutes (1;17) is controlled by signals from camera units (7;13), which signals are analyzed by a computer unit, whereby the particles at the consecutive second feeding chute are separated before they fall out over the edge at the open end of the consecutive second feeding chute, characterized in that the measuring device comprises that - each feeding chute (1;17) has a means for generating vibrations at controlled frequency (19;12), - a first set of a first camera unit and a first light source arranged below the first feeding chute, - a second set of a second camera unit and a second light source arranged below the second feeding chute, wherein - both the first set of a first camera unit and a first light source and the second set of a second camera unit and a second light source is placed so that the particles (2;18) fall freely through the optical path between a camera unit (7;13) and a light source (8;15) of a respective set, - the means for generating vibrations at controlled frequency (19;12) and the camera units (1;13) are connected to a computer unit, - the computer unit is adapted to - receive the signals from the camera units (7;13) and analyze said signals in order to control the means for generating vibrations at controlled frequency (19;12), and - adapted to analyse the densities of the particles on the respective feeding chute (1:17) and to analyse the size distribution of particles in a sample, and - the means for generating vibrations at controlled frequency (19;12) are adapted to control the vibration speed of each of the first and the second feeding chutes independently. - a first feeding chute and a consecutive second feeding chute, - the first feeding chute and the consecutive second feeding chute are arranged so that the first feeding chute is arranged above the consecutive second feeding chute, so that the particles of a flow of particles that falls from a free open end of the first feeding chute are controlled in order for said particles to be delivered in free fall onto the consecutive second feeding chute, - the feed rate of the feeding chutes (1;17) is controlled by signals from camera units (7;13), which signals are analyzed by a computer unit, whereby the particles at the consecutive second feeding chute are separated before they fall out over the edge at the open end of the consecutive second feeding chute, characterized in that the measuring device comprises that - each feeding chute (1;17) has a means for generating vibrations at controlled frequency (19;12), - a first set of a first camera unit and a first light source arranged below the first feeding chute, - a second set of a second camera unit and a second light source arranged below the second feeding chute, wherein - both the first set of a first camera unit and a first light source and the second set of a second camera unit and a second light source is placed so that the particles (2;18) fall freely through the optical path between a camera unit (7;13) and a light source (8;15) of a respective set, - the means for generating vibrations at controlled frequency (19;12) and the camera units (1;13) are connected to a computer unit, - the computer unit is adapted to - receive the signals from the camera units (7;13) and analyze said signals in order to control the means for generating vibrations at controlled frequency (19;12), and - adapted to analyse the densities of the particles on the respective feeding chute (1:17) and to analyse the size distribution of particles in a sample, and - receive the signals from the camera units (7;13) and analyze said signals in order to control the means for generating vibrations at controlled frequency (19;12), and - adapted to analyse the densities of the particles on the respective feeding chute (1:17) and to analyse the size distribution of particles in a sample, - the means for generating vibrations at controlled frequency (19;12) are adapted to control the vibration speed of each of the first and the second feeding chutes independently.