Abstract: A linear actuator and pump unit for precision displacement of fluids in which a positive displacement, piston pump is coupled to an actuator mechanism having a carriage on a guide that is displaced by a rotary drive connected to a take-up drum on an anchor structure that has a pulley line anchored to the anchor structure looped around a first idler pulley on the carriage, looped around an idler pulley on the anchor structure, looped around a second anchor structure on the carriage, and connected to the take-up drum, the positioning of the carriage being detected by a sensor and the rotary drive that controls the precision operation of the piston pump.