VERSATILE FLOW RATE CONTROLLER

摘要

A fluid-switchable flow rate control system that permits free changing of the full scale flow rate and which can control a plurality of kinds of fluids with high precision. The fluid-switchable flow rate control system controls the flow rate of fluid with the pressure P1 on the upstream side of the orifice member held about twice or more higher than the downstream pressure P2, the fluid-switchable flow rate control system comprising an orifice member 8 replaceable with another to provide a suitable orifice diameter according to the kind of fluid and the flow rate range, a control valve 2 provided on the upstream side thereof, a pressure detector 6 provided between the control valve 2 and the orifice member 8, and a flow rate calculation circuit 14 where, from the pressure P1 detected by the pressure detector, the flow rate Qc is calculated by the equation Qc = KP1 (K: constant), a flow rate-setting circuit 16 for outputting flow rate setting signal Qe, a flow rate conversion circuit 18 for multiplying the calculated flow rate signal Qc by the flow rate conversion rate k into switch-over calculated flow rate signal Qf (Qf = kQc) to change the full scale flow rate, and a calculation control circuit 20 to output the difference between the switch-over calculation flow rate signal Qf and the flow rate setting signal Qe as control signal Qy to the drive 4 of the control valve 2, thereby opening or closing the control valve to bring the control signal Qy to zero, thus controlling the flow rate on the downstream side of the orifice member.