Syringe type displacement pump:

These pumps work through positive solvent displacement by a mechanically driven piston at a constant flow rate. The piston is actuated by a screw feed drive through a gear box usually run by a digital stepping motor. The rate of solvent delivery is controlled by changing the voltage of the motor. The solvent chamber has finite capacity of 250-500 mL which may be refilled if required be. Pulse less flow is achieved along with high pressure capability of 200-475 atm.