Fluid Metering Inc.’s STH and STQ Ratio:Matic Duplex pumps consist of two FMI valveless pump heads direct coupled to a single variable speed drive, a standard 23-frame stepper motor although other drive types can be used. The displacement of each pump head is independently adjustable, and a variety of pump head sizes can be used in combinations to achieve dispensing ratios from 1-to-1 up to 500-to-1. Typically, each pump head is calibrated at the factory, locked in place, and will not require recalibration in the field, even after millions of cycles. Models are also available that can be adjusted in the field for applications that require frequent changes in mixing ratios or dispense volumes. The pumps feature FMI’s CeramPump valveless piston pump technology. This pump design utilizes one moving part, a rotating and reciprocating ceramic piston to accomplish both pumping and valving functions without valves. The piston and mated liner are made of dimensionally stable, sapphire-hard ceramics, which ensure long-term, drift-free accuracy of 1 percent or better for millions of maintenance-free cycles. These pumps can be used for precision mixing, diluting, and proportional metering for OEM medical, analytical, and industrial instrumentation.