Abstract: A control system for a particle detector for detecting particles of blood components in an electrolyte employs sets of cams mounted on one-way clutches, which are positioned on a shaft of a motor. When the shaft is rotated by the motor in a clockwise direction, one set of cams moves together with the shaft, and when the shaft is rotated in the counterclockwise direction, another set of cams rotates in the counterclockwise direction. The rotation of cams controls movement of pistons which, together with cavities, form syringes and valves interconnected with passages. The valves and syringes are operated in sequence to prepare a specimen for measurement, to perform the measurement, and to clean up and purge the system between measurements.