Masoneilan SVI3 Installation and Maintenance Manual
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2.3 Physical and Operational Description
The SVI3 is housed in an industrial, tough, weatherproof, corrosion resistant aluminum
housing that has been designed for operation in hazardous areas. Electrical connections
are made through two 1/2" NPT conduit entries. Pneumatic connections are made
through two ¼" NPT ports.
2.3.1 Principle of Operation
The SVI3 is a smart electro-pneumatic positioner that:
1. Receives a 4 - 20 mA electrical position setpoint signal from the controller and
compares the position setpoint input signal to the valve position feedback sensor.
2. Uses the difference between the position setpoint and position feedback is analyzed
by the position control algorithm to set a servo signal for the I/P converter.
3. Processes the I/P output pressure and amplifies it by using a pneumatic relay that
drives the actuator.
4. Assures the error between the setpoint and the valve position feedback is within
range, no other correction is applied to the servo signal in order to maintain valve
position.
Figure 2 Block Diagram with I/P Converter and Pressure Sensor
Power
HART
Posion Setpoint
Characteriscs
Diagnoscs
Non – Linear PID
Posion Control
Magnecally
Coupled Hall-Effect
Posion Sensor
Display
Flow Regulator
I/P
Current to Pressure
Converter
Pneumac Relay
DA
Filter
Input Current, 4
to 20 mA
Electronics
Air Supply
PS
I
P
P1
Actuator
Pressure Sensor
