A construction of particle counter by using laser light scattering

A simple particle counting system was constructed by using laser light scattering technique. The main components consist of a 50 mW green laser diode (lambda = 532 nm) and a Hamamatsu H5784 photomultiplier tube (PMT). The intensity of scattered light from a particle was measured with a PMT. The pulse height from a PMT is proportional to the size of a particle. The silica powder with the size of 75 mum, 100 mum and 150 mum were used as reference particles, winnowed by sieve and measured by image analyzer to ensure the reference size. Resulting in the pulse height of 100 mV, 200 mV and 400 mV respectively, from a PMT. The experimental results showed that an implementation of particle counter can be used to measure a quantity as well as an approximate size of the particles.