| 摘要 |
A self-contained valve positioner having a single valve positioner housing including an actuator portion and having a pneumatically operated actuator unit therein carrying a main valve member to position the main valve member relative to a main valve seat in a valve unit in relation to the magnitude of a single pneumatic signal directed to the valve positioner and being utilized as the fluid source therein for pneumatically operating the actuator unit, the actuator unit having structure in the housing to cause the actuator unit to progressively open the valve member as the signal being directed to the valve positioner progressively increases from a first value to a second value and thereafter to progressively close the valve member as the signal being directed to the valve positioner progressively increases from the second value to a third value.
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