Both diaphragm and piston pumps are used for dosing liquids, but differ in the way this is done.
The former uses a flexible membrane that moves back and forth to suck in and dose the liquid. When this moves inwards, it creates a negative pressure inside the head, sucking the liquid in. When the membrane moves outwards, the liquid is pushed out of the pump.
The second uses a piston moving back and forth inside a hydraulic head. When the piston moves inwards, it creates a negative pressure inside the cylinder, sucking the liquid out. When the piston moves inwards, the liquid is pushed out of the cylinder.
In general, the diaphragm pump is preferable when dosing abrasive or low-viscous liquids. The piston pump is usually more efficient with viscous liquids in systems requiring high operating pressure.
