Positioner

A positioner for driving a regulator valve by converting an inputted electric signal into a pneumatic signal, comprising:

• electronic circuitry configured to process electric signals;
• an electropneumatic converter configured to convert, into pneumatic signals, electric signals that have been processed by the electric circuit module;
• an explosion proof container configured to contain, in an interior space, the electric circuit module and the electropneumatic converter;
• and
• a pneumatic amplifier, configured to be provided outside of the explosion proof container, that amplifies the pneumatic signal converted by the electropneumatic converter, wherein:
• the explosion proof container comprises a two-laver structure and is formed with air flow paths for the air that is fed into the pneumatic amplifier and the air that is fed out of the pneumatic amplifier, in a thick portion between an inner wall face and an outer wall face of the container that encompasses the surrounding of the interior space;
• the inner wall face is separate from the outer wall face and forms a gap in between;
• the air flow paths are formed along an inner wall face of the explosion proof container;
• and
• the inner wall face of the explosion proof container where on the air flow path is formed is arc-shaped or a shape that uses many curved faces of free curve shapes.