Analyzing and Processing the Malfunction of Control Valve

The control channel of the valve is installed as shown in Fig. 1, DCS output
4–20 mA control command that send to the positioner though local CR box. The
positioner and position sensor form a closed control loop. The positioner receiving
setpoint from DCS. At the same time, it acquires valve position feedback signal
from sensor, then after internal PID operation output signal to drive the actuator
control valve actuation.
Positioner electronic module consist of a multiplexer, an A/D converter, a D/A
converter, a temperature sensors, a Hall-effect position sensor (or a slide rheostat), a
pressure sensor, a microprocessor and a power distribution management circuit. The
diagram of functional block.