Computer-controlled Teflon flow control valve

A butterfly vane valve is described for the servo control of a gas or liqui d flow. The valve is suitable for reactive species since nearly all wetted parts are Teflon. The valve is operated by a servo motor that is controlled by a dedicated microprocessor programmed in BASIC. The valve offers many o ther desirable features, including constant and relatively small surface ar ea, low dead volume, high conductance in the full-open position, vacuum com patibility, firmware control, and scalability. (C) 1999 American Institute of Physics. [S0034-6748(99)03812-5].