Type 3285

12 | 15

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7.

Product operation

Standard on/off valve

In the ON/OFF variant, an external voltage signal is digitized and the valve is closed or opened. The status of the two end positions of the

valve are indicated on the LED. In addition, the valve position “closed” is reached via the digital output.

Standard control valve

The standard proportional valve converts an external standard signal (position set-point value) into a valve position. Both valve end

positions are indicated by the LED status. Additionally, the digital output indicates when the “closed” valve position has been achieved.

Process diagram

Description

Valve

opening

Electromotive

actuator

Position sensor

Positioner

Set-point

position

CMD

CTRL

POS

Z1

POS

Position control loop

+ -

Valve

body

Xd1

Positioner variant

The proportional valve in the position control variant converts an

external standard signal, the position set-point value, into a valve

position. The position of the actuator is controlled according to the

set-point position. The position sensor records the current position

(POS) of the electromotive valve. This actual position is compared

by the positioner with the set-point value (CMD) specified as the

standard signal. If there is a control difference (Xd1), a motor control

signal is given to the actuator as the actuating variable. Z1 is a

disturbance value.

The two end positions of the valve are indicated by the LED status.

In addition, the actual position recorded by the position sensor is

output via the M12 circular plug-in connector.

Process

controller

Position

control loop

SP

CMD

Z2

PV

Measured

quantity

+

Xd2

-

Transmitter

Process

Process

set point

value

Valve

opening

Process controller variant

The additionally implemented PID controller can perform not only

the actual position control but also a process control in the sense of

a cascade control.

The process controller is integrated into a control loop. The position

setpoint of the valve is calculated from the process setpoint and the

actual process value via the control parameters (PID controller). The

process setpoint can be specified by an external signal.

During the process control the position control mentioned above

becomes the subordinate auxiliary control circuit; this results in a

cascade control. The process controller in the main control circuit

has a PID function.

The process set-point value (SP) is specified as a set-point value

and is compared with the actual value (PV) of the process variable

to be controlled. The position measuring system records the current

position (POS) of the electromotive linear actuator. This position

actual value is compared by the position controller with the

set-point value (CMD) specified by the process controller. If there is

a control difference (Xd2), the actual position (POS) and therefore

the valve opening are changed by the control variable (CTRL). Z2

represents a disturbance variable.