Positioners, controllers and sensors
Overview
The accuracy of any pneumatic control system depends on how well the final valve follows the incoming signal. Line pressure changes, stem friction, differential pressure shifts and diaphragm hysteresis can all create positioning error if the actuator is left to respond without feedback correction. A positioner compares the control signal with the actual valve position and adjusts the pneumatic output to the actuator accordingly, helping the valve reach and hold the demanded position more consistently. That correction improves loop stability, repeatability and valve response, particularly on variable-load duties where pressure conditions and process demand do not stay constant. Smart positioners also add diagnostics, communication and commissioning visibility, making them useful where the valve package needs better feedback for maintenance and operating decisions rather than simple air-to-open movement alone. The broader Spirax Sarco offering also includes controllers, interface devices and sensors that help turn the valve package into a coordinated control system rather than a collection of isolated hardware items.
Related feedback and valve-package routes
Feedback hardware becomes useful only in the context of the final valve assembly. Continue into steam control valves when the positioner choice depends on the installed valve duty, and use pneumatic actuators when the immediate comparison is actuator format rather than signal hardware.
If the project is moving toward lower routine air use or electric drives, compare electric actuators.
SP400 positioner
SP400 positioner now has a dedicated model page for 4-20 mA input, linear or rotary pneumatic valve applications, setup checks and enquiry guidance.
SP7 positioners
SP7-10, SP7-11 and SP7-12 positioners now have a dedicated model page for communication routes, technical documents, SP7 Pro and hazardous-area package options.
SX80 process controller
SX80 process controller now has a dedicated model page covering 1/16 DIN panel mounting, universal input/output, PID auto-tuning, quick code configuration and installation documentation.
SP500 smart positioner
SP500 smart positioner now has a dedicated model page for enhanced 4-20 mA input, optional HART communication, diagnostic data logging, auto commissioning and installation documentation.
EP5 electro-pneumatic positioner
EP5 electro-pneumatic positioner now has a dedicated model page covering 4-20 mA and 0.2-1.0 bar input signals, single-acting actuator compatibility, ISP5 explosion-proof option and installation manual.
EP500 electro-pneumatic positioner
EP500 standard electro-pneumatic positioner now has a dedicated model page for 4-20 mA input, split-range capability, integral pressure gauges, central or offset mounting and installation documentation.
Continue your instrumentation selection
Accurate modulation depends on more than the actuator alone. Positioners, controllers and sensors determine how well the valve package interprets, follows and reports the control signal.
See the wider controls context
Return to the wider control systems range when the instrumentation choice is part of a broader control hardware or system architecture decision.
Match feedback to the actuator package
Use pneumatic actuator pages when the next step is choosing the air-powered actuator platform that the positioner or controller will manage.
Build the complete control valve assembly
Review control valves when you need to connect positioner choice with valve trim, duty conditions and the final valve assembly.