The RCV Plus™ Gas Mixing System is a combination of flow meters specifically designed to monitor and control the ratio of two gases. It consists of an RCV Plus™ (Waukee Ratio Control Valve) and a FLO-TRONIC Plus™ (Waukee Flow-Meter). The RCV Plus™ utilizes a micro-processor that continuously compares a preset ratio to the real time ratio of the two gas flows as measured by the FLO-TRONIC Plus™ and the ratio control valve itself. Using a stepper motor, the RCV Plus™ continuously adjusts the flow metering needle-valve to precisely maintain the preset gas ratio. The real-time ratio is continuously displayed on the LCD screen of the RCV Plus™. Included in the RCV Plus™ is an optional input for the addition of a trim gas, which is frequently used for process control. Trim gas addition is additive to the ratio. When trim gas is used, the continuously displayed real-time ratio then includes the trim gas addition.