Free-piston device for measuring flow rates, esp. in dialysis machines - in which two cylinders and pistons of different volumes are used, and measuring and protection systems with separate piston-position sensors operate valves and provide output signal

摘要

A free-piston device for measuring flow rates in ultrafiltation processes uses two cylinders and pistons and has the novel feature that the cylinder/piston combinations (2, 17) have different displacement signal to a measuring system (14, 15) while a further sensor (4, 22) give separate similar signals to an independent protection system (10, 11). Signals from both systems are used for controlling the inlet and outlet valves (13, 18) and as inputs to the supervisory system (23). USE/ADVANTAGE - Esp. in dialysis machines (1). A high degree of accuracy is achieved under conditions of temp. variations in the range 10 to 100 deg. C, in particular when measuring very small volumes such as in dialyses involving young children.