Apparatus for measuring particle size distribution by making use of laser beam diffraction and scattering

Claim 1

An apparatus for measuring a particle size distribution through the measurement of intensity distribution of light rays scattered from particles irradiated with a laser beam, said apparatus comprising: a transparent sample vessel for accepting a fluid medium suspending therein sample particles whose size distribution is to be measured, said transparent sample vessel being irradiated with a laser beam; a first photosensor assembly consisting of a plurality of concentrically arrayed semicircular photosensors for detecting the intensity distribution of light scattered forward by said sample particles; a second photosensor assembly consisting of photosensors for detecting lights scattered at angles larger than the scattering angle of said light scattered forward; a first temperature sensor for sensing the temperature T₁ of said first photosensor assembly; a second temperature sensor for sensing the temperature T₂ of said second photosensor assembly; means for generating an alarm signal when a temperature variation ΔT₁ of said first photosensor assembly, a temperature variation ΔT₂ of said second photosensor assembly or a temperature difference |T₁ - T₂| between said first and said second photosensor assemblies reaches or exceeds a predetermined value.