PURPOSE: To make precise classificating counting of different size particles, by furnishing the circuit such as to delay some fixed time the detecting of the small particles when the detecting signal of the big particles is generated during the particles in the particle suspension are passing through the fine hole.

CONSTITUTION: The main body 1 of the detector of particle numbers counting device is made of synthetic resins and furnished at the tip the pellet 4 made of stainless steel which has a fine hole 3, and is connected to the inner fine tube made of stainless steel and is electrically connected through the screw 10 of metal fitting 8. Upper part 14 is connected to the suction pressure through electro-magnetic valve 16. The signal detected by the detecting circuit 25 passes the pulse of big particle by the upper level threshold circuit 27 and at the same time sends stop signal to the low level threshold circuit 30 and giving the delay of the prescribed time to the pulse signal from the detecting circuit through the delaying circuit 28, passes the pulse after the big particles are discharged. Passed pulses are counted at the counting circuit 33, and the precise classificated counts of big and small particles are indicated on the indicator circuit 34, 35.