Burkert Type 8635 - Manual (Page 19)

8635 - 17
S
YSTEM
D
ESCRIPTION
(S/HART)
The SIDE Control (S/HART controls the position of the pneumatic actuator, whereby the position sensor
measures the actual position (POS) of the actuator. The controller compares this actual value of the
position with the setpoint (CMD), which is presented as a standard signal. If a control difference (Xd1)
exists, a pulse-width modulated voltage signal is sent to the positioning system as the correcting variab-
le. If the difference is positive, the pressurizing piezoelectric valve is driven via output B1; if it is negative,
the exhausting piezoelectric valve is driven via output E1. In this way, the position of the actuator is
altered until the control difference is 0. Z1 represents a disturbance.
Operation as a positioner (S/HART)
Position sensor
Position
setpoint
Positioner Positioning system
(piezoelectric valves) Continuous
valve
Valve opening
Position control loop