Self-operated regulator

Controllers which acquire sufficient force from the measurement to move the actuator do not require auxUiary power. Such controllers have a simple and durable construction, and many combine measuring instrument, controller, and actuator 

Here the exit pressure affects a diaphragm and holds a valve in an equilibrium position against the force of a spring. If the pressure rises, this closes the cross-section of the plug against the seat, and if the pressure lowers it opens again. This is also the method of operation of the pressure controllers in pneumatic transmission lines. Supply pressure-reducing valves are controllers without auxiliary power. 

Single-loop controllers with auxiliary power use compressed air or, more commonly now, electrical power to receive and transmit signals. These devices are much more accurate than those without the auxiliary power also they are not integrated in the measurement apparatus or the actuator. Distributed control systems are rapidly replacing the single-loop controller panel boards unless only a small number of control loops are involved. 

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Reduced set-point offset with increasing load flow can be achieved by adding a pitot tube to the self-operated regulator. The... 

Self-Operated Regulators Self-operated regulators are the... 

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