Control systems > Positioners, controllers and sensors
Spirax Sarco SP400 Positioner
The Spirax Sarco SP400 is a loop-powered electro-pneumatic valve positioner for linear and 90 degree rotary pneumatic valves. It uses a 4-20 mA input signal, non-contact valve position feedback and automatic air output correction to help the valve reach and hold the demanded position.
Quick facts
Where SP400 sits in the control range
SP400 belongs in the Spirax Sarco positioners, controllers and sensors range. It is intended for pneumatic control valve duties that need position feedback, straightforward setup and low steady-state air consumption without a more complex communication package.
Compared with SP500, SP400 is the simpler option for standard positioning duties where 4-20 mA input, digital setup and reliable feedback are the main requirements.
Product characteristics
SP400 uses the input current signal to set the valve position, then compares that demand with valve position feedback and adjusts the actuator air output. This closed-loop correction helps overcome stem friction and process forces so the valve can hold the requested opening more consistently.
The non-contact feedback arrangement reduces mechanical linkage between valve and positioner, while piezo valve technology helps reduce steady-state instrument air use. Setup is supported by push buttons, an LCD menu and automatic commissioning routines.
Typical selection checks include actuator style, mounting standard, valve action, requirement for a pressure gauge block, air preparation quality and whether the positioner is being ordered alone or as part of a complete control valve package.
Related routes
- Return to positioners, controllers and sensors to compare SP400 with adjacent feedback and control products.
- Review pneumatic actuators when the immediate decision is the actuator platform.
- Review control valves when the valve body, actuator and positioner need to be selected together.
Continue your SP400 selection route
SP400 selection usually sits inside a pneumatic valve package decision that also includes the actuator, valve body, instrument air and commissioning requirements.
Compare the positioner range
Return to positioners, controllers and sensors when you need to compare SP400 with SP500, SP7, EP500, EP6 and other feedback products.
Match the pneumatic actuator
Review pneumatic actuators when the next step is confirming linear or rotary motion, mounting interface and direction of action.
Build the complete valve package
Use control valve pages when the project needs the valve body, actuator, positioner and air preparation package considered together.