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SITRANS VP300 Positioner 6DR6 Series - 6DR6 310-1NA10-0AA0

The SITRANS VP300 works by using a non-contacting giant magnetoresistance (GMR) principle to detect the valve's position. A magnet attached to the valve's stem or shaft moves with it, and its magnetic field is detected by sensors in the positioner, which then sends a pneumatic signal to a diaphragm actuator. This process allows the positioner to precisely control the valve's position based on an external command signal and provide feedback.

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Detailed working principle

Position Detection: A magnet is attached to either the linear spindle or the rotary shaft of the actuator. As the valve stem or shaft moves, the magnet's position changes.
GMR Technology: Integrated sensors in the positioner use the giant magnetoresistance (GMR) principle to detect the position of the magnet without physical contact. This method is very robust, resists magnetic fields and temperature fluctuations, and is less sensitive to vibration.
Signal Processing: The GMR sensors convert the magnet's position into a signal that can be interpreted by the positioner's internal electronics.
Actuator Control: The positioner compares the detected valve position with the desired setpoint from a controller. If there is a difference, the positioner sends a pneumatic signal to the actuator to move the valve stem to the correct position.
Feedback Loop: The positioner continuously monitors the actual valve position and adjusts the pneumatic signal to the actuator until the valve is in the desired position, creating a closed-loop control system.
Installation: For easy installation, the VP300 is designed to work with a single magnet and can be mounted using the OPOS Interface, which requires only two screws for attachment.

Its working principle can be broken down into three main stages:

Signal Reception and Comparison:

The positioner receives a 4-20 mA setpoint signal from a control system (DCS, PLC, etc.).
This electrical signal is processed by an internal microcontroller, which determines the desired valve position.
Simultaneously, the actual position of the valve stem or shaft is continuously measured using a non-contacting sensor based on the Giant Magnetoresistance (GMR) effect. A magnet attached to the actuator's moving part interacts with the sensors in the positioner to provide highly accurate position feedback without mechanical wear.
The microcontroller electronically compares the setpoint (desired position) with the actual position.

Pneumatic Control:

If a deviation is detected between the desired and actual positions, the microcontroller uses a control algorithm to actuate the internal pneumatic valve block.
The pneumatic block then precisely doses compressed air into, or removes air from, the chamber(s) of the pneumatic actuator (for single or double-acting actuators).
This change in air pressure causes the actuator to move the valve stem or shaft, adjusting the valve's opening.

Feedback and Continuous Adjustment:

As the actuator moves, the GMR sensor continuously monitors the new position and feeds it back to the microcontroller.
This creates a closed-loop control system, allowing the positioner to make continuous, precise adjustments until the actual valve position matches the setpoint signal, regardless of external disturbances like changing differential pressures or friction.

Key Features Related to its Working Principle

GMR Position Sensing: This non-contacting technology makes the positioner highly resistant to vibration and eliminates mechanical linkages susceptible to wear, ensuring long-term reliability and accuracy.
Microcontroller-based Control: The digital control allows for advanced functionalities such as customizable flow characteristic curves, extensive diagnostic functions (e.g., monitoring static friction, deadband, operating hours), and partial stroke testing (PST).
HART Communication: The positioner supports HART communication, allowing remote parameterization, monitoring, and diagnostic data retrieval via systems like SIMATIC PDM.
OPOS Interface®: This mechanical interface allows for simple and fast installation using only two screws and integrated piping, simplifying maintenance.

Full Datasheet