Masoneilan SVI-3 Positioner SVI-3 Series - SVI3 2122121

The Masoneilan SVI-3 works by receiving a 4-20mA control signal and using advanced algorithms to precisely control the air pressure to a pneumatic valve actuator. It uses a non-contact magnetic sensor to measure the valve's position feedback, which is then compared to the input signal to adjust the pneumatic output. The SVI-3 features automated commissioning, local user interface, and low-bleed pneumatics for energy efficiency and ease of use.

Detailed breakdown of the working principle:

• Receives input: The SVI-3 takes a standard 4-20mA control signal from a control system. It also uses HART communication for configuration and diagnostics.
• Measures valve position: A non-contact magnetic sensor continuously measures the exact position of the valve stem or actuator.
• Compares and computes: The digital positioner compares the actual valve position with the desired position from the input signal. Advanced algorithms then calculate the precise pneumatic output needed to move the valve to the correct position.
• Controls pneumatic output: The SVI-3 uses a two-stage pneumatic system to precisely control the air pressure being sent to the valve's actuator. This allows for accurate and responsive control of the valve's movement.
• Provides feedback: The SVI-3 provides feedback on the valve's status through its local display, digital communication, and online diagnostic features, which can be accessed through software like ValveView.

Key features that enhance its operation:

• SmartCal: An automated, single-button "SmartCal" function simplifies the setup process.
• Low-bleed pneumatics: The design minimizes air consumption, which reduces energy usage and emissions compared to conventional positioners.
• Modular architecture: The modular design makes it easy to upgrade and service in the field.
  Integrated diagnostics: Built-in online valve diagnostics and data storage allow for proactive maintenance and better overall plant efficiency.

Working Principle

The core working principle involves a closed-loop control system that continuously compares the desired valve position (setpoint) with the actual valve position (feedback) and adjusts the air pressure to the actuator accordingly.

1. Input Signal: The SVI-3 receives a standard 4-20mA analog input signal from a control system (DCS or PLC), which represents the desired valve position (setpoint). This signal also carries digital HART communication for configuration and diagnostics.
2. Position Sensing: The actual position of the valve stem or shaft is measured using a robust, non-contact magnetic position sensor system. This technology is fully sealed from the environment, ensuring reliable performance in harsh conditions.
3. Microprocessor Control: A built-in microprocessor runs advanced control algorithms to compare the input setpoint to the position feedback from the sensor.
4. Pneumatic Control: Based on this comparison, the microprocessor modulates the flow of compressed instrument air using a two-stage pneumatic system.

• If the actual position does not match the setpoint, the internal pneumatic components (like a spool valve or similar mechanism) increase or decrease the air pressure supplied to the actuator.
• The positioner features low bleed pneumatics to reduce air consumption while maintaining precise control and quick response.

5. Actuator Movement: The change in air pressure causes the pneumatic actuator (either linear or rotary) to move the valve stem/shaft until the non-contact sensor indicates the correct position has been reached.
6. Diagnostics and Communication: The positioner continuously monitors the valve's performance and health using embedded online diagnostics and stores data for up to a year. This information can be accessed via HART communication and specific software (like ValVue) for predictive maintenance and troubleshooting.

In essence, the SVI-3 translates an electrical control signal into a precise pneumatic output, ensuring the control valve maintains the exact position demanded by the control system.

 Full Datasheet

Positioner Transmitter Feature  

• Manufacturer: Masoneilan SVI-3
• Product No. : SVI3 2122121                                                                                                                  
• SVI3 - SVI3- Smart Valve Interface - 3rd Generation
• Diagnostics: 2 - Advanced Diagnostics
• Pneumatic Train / Capacity / Fault State: 1 - Single Acting, Standard Flow (Cv >=0.5), De-energize on fault (Fail Safe)
• Instrument Air / Temperature: 2 - Compressed Air Only, Extreme Temperature (-55°C to 85°C), Silicone Diaphragms
• Construction / Display: 2 -Aluminum / Display with local interface
• Communication: 1 - 4-20mA - HART® Communication Protocol
• Input/Output Options 2 -  4-20mA Analog Output (Position Retransmit) Quantity (1)
• Agency Approvals: 1 - Hazardous Area Unilable (ATEX, IECEx, US, Canada, UKEX, EQM, RCM, CMIM)
• None: 0 

There are several Model of positioner, for more details read the PDF below 

Basic Ordering Information