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A miniature flow controller housing a fluid inlet and a fluid outlet, with the inlet pressure exceeding the outlet pressure. The outlet has orifices defined in a crystalline silicon membrane, along crystal planes of the silicon so that the geometry of the orifices is precisely known. The inlet and o

A miniature flow controller housing a fluid inlet and a fluid outlet, with the inlet pressure exceeding the outlet pressure. The outlet has orifices defined in a crystalline silicon membrane, along crystal planes of the silicon so that the geometry of the orifices is precisely known. The inlet and outlet are throttled by poppets which can seal the orifices on command of a device controller. The poppets are driven by shape retentive membranes which have two states, an open state and a closed state with a state change caused by application of small amounts of current to a resistive element in contact with the membrane. Rapid actuation of the poppets causes operation of the valve in a pulse mode. Where the fluid is a gas, pressure and temperature transducers measure conditions inside of the housing for application of gas law principles. By recording instantaneous pressure and temperature in the chamber, as the poppets are actuated, mass flow through the outlet orifices of the chamber is computed.

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[ What is claimed is:] [1.]1. A flow controller comprising,a housing of known volume having an inlet orifice connected to a fluid supply and an outlet delivering a fluid supply, the inlet pressure greater than the outlet pressure, the outlet having a crystalline membrane defining an orifice of preci

[ What is claimed is:] [1.]1. A flow controller comprising,a housing of known volume having an inlet orifice connected to a fluid supply and an outlet delivering a fluid supply, the inlet pressure greater than the outlet pressure, the outlet having a crystalline membrane defining an orifice of precisely known dimensions, the housing supporting reciprocating orifice closure members driven by actuators opening and closing the inlet orifice and the outlet orifice upon command,a pressure and a temperature transducer mounted in the housing, the transducers productive of electrical signals representing pressure and temperature in the housing,a device controller electrically connected to the actuators and receiving the electrical signals from said transducers and from an input set point and flow start and end signals, the device controller signaling the actuators to open and close the inlet orifice and outlet orifice whereby a desired fluid flow through the housing is maintained. [15.]15. A method of controlling gas flow,providing a housing with a gas inlet orifice and a gas outlet orifice, the gas inlet orifice communicating with a gas supply with a pressure greater than that in the housing,modulating gas pressure at the gas inlet orifice about a setpoint wherein pulses of gas enter the housing,modulating gas pressure at the gas outlet aperture about said setpoint wherein pulses of gas exit the housing,coordinating the duration of the outlet pulses with the inlet pulses in a time variable manner wherein the duration of said outlet pulses produce the desired gas flow.16. The method of claim 15 wherein the modulating of gas pressure is by opening and closing orifices in the housing.17. A method of controlling gas flow,providing a housing with a pulsatile gas inlet orifice and a gas outlet orifice, the gas inlet orifice communicating with a gas supply with a pressure greater than that in the housing,determining a gas flow rate at the gas outlet orifice for gas at various temperatures and pressures for an outlet orifice of specified size,calculating a set point pressure within the housing for a selected gas outlet flow at a specified temperature and pressure in view of the determined flow rate through said outlet aperture, anddetermining a fill time ratio t.sub.d /t.sub.f expressing the time the inlet valve is open, t.sub.d, relative to the time it is closed, t.sub.f, for inlet gas pulses.18. A method of controlling gas flow,providing a housing with a pulsatile gas inlet orifice and a gas outlet orifice, the gas inlet orifice communicating with a gas supply with a pressure greater than that in the housing,determining a gas flow rate at the gas outlet orifice for gas at various temperatures and pressures for an outlet orifice of specified size,calculating a set point pressure within the housing for a selected gas outlet flow at a specified temperature and pressure in view of the determined flow rate through said outlet aperture,for a measured fill time t.sub.f and a drain time t.sub.d, where t.sub.d is less than t.sub.f for even gas flow at specified temperatures and pressures, determining the number of t.sub.f and t.sub.d cycles per minute to achieve a selected flow rate, andcounting the number of t.sub.d and t.sub.f cycles to achieve the selected flow rate.