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Fiche 1,  Justifications,  Anglais

Record number: 1, Textual support number: 1 CONT

When specifying a mass flow control system, the first consideration is whether the process will take place at constant system pressure, constant throughput, and/or predetermined gas flow ratio. Another important consideration is whether system control will be automatic (microprocessor) or manual (setpoint potentiometers). ... There are three major state-of-the-art systems that can be identified. The first uses a flowmeter(s) ... as the primary transducer(s) to monitor mass flow. Using this format, a signal is compared in control circuitry to a setpoint signal. This generates an error voltage which is used to drive a valve, thus continuously controlling the flow. The second major type of system uses a pressure transducer as the primary sensing element. System pressure is held either constant or varied at a predetermined rate by controlling the mass flow rate of process gases. This leads to a third type of system that slaves valves and flowmeters to the primary sensing.  1, fiche 1, Anglais, - mass%20flow%20controller

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