Mcgraw-edison Company

Eric V Anderson

Robert Claude Prescott

Calman Gold

A transducer for converting an electrical current signal to a pneumatic pressure. A solid state element such as piezo-electric flapper element 48 is used to vary the pressure drop through a nozzle 46 to provide a controlled pressure supply 28. A micro-power electronic circuit 59 controls the flapper. A solid state pressure sensor 24 detects the output pressure and provides a feedback signal for use in a negative feedback loop to control the flapper element. The flapper element may be triangularly shaped to reduce its responsiveness to relatively low frequency mechanical vibrations. In a exemplary embodiment, where intrinsic safety requirements limit terminal voltages, the flapper element is driven by a transconductance amplifier 94 which is powered through a shunt regulator 82 and a voltage tripler 92. The shunt regulator provides operating potentials which are derived from the signal current.

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Greenacres, WA, United States of America

Eric V Anderson