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
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.
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.
The Spirax Sarco SX80 is a 1/16 DIN panel mount process controller offering universal input for RTD and thermocouple signals, universal output with VMD 3-point, 4-20 mA analog, relay and logic, PID auto-tuning, 3 setpoints and a built-in 18 VDC transmitter power supply.
Spirax Sarco SP7-10, SP7-11 and SP7-12 smart positioners control pneumatic linear or rotary actuators and support 4-20 mA, HART, PROFIBUS PA or Foundation Fieldbus communication routes.
The Spirax Sarco SP500 is an enhanced loop-powered electro-pneumatic smart positioner for linear and rotary pneumatic valves. Building on the SP400 platform, it adds optional HART communication, diagnostic data logging, retransmission capability and a 24V power board, while retaining the same 4-20 mA input, Hall effect non-contact feedback and piezo valve technology.
The Spirax Sarco EP500 is a standard electro-pneumatic positioner for linear and rotary pneumatic control valves. It uses a 4-20 mA input signal with split-range capability, integral pressure gauges, central or offset mounting and a quick-fit electrical connection cap to deliver reliable position feedback correction without the communication and diagnostic features of the SP400 and SP500 smart positioners.
| Document | Reference | Language | Download |
|---|---|---|---|
| SP400 Electropneumatic Smart Positioner | IM-P343-37-US | English | Download |
SP400 selection usually sits inside a pneumatic valve package decision that also includes the actuator, valve body, instrument air and commissioning requirements.
Return to positioners, controllers and sensors when you need to compare SP400 with SP500, SP7, EP500, EP6 and other feedback products.
Review pneumatic actuators when the next step is confirming linear or rotary motion, mounting interface and direction of action.
Use control valve pages when the project needs the valve body, actuator, positioner and air preparation package considered together.
