Design And Principle Of Operation - Samson 3730-5 Mounting And Operating Instructions

3 Design and principle of oper-
ation
The positioner is mounted on pneumatic con-
trol valves and is used to assign the valve
position (controlled variable x) to the control
signal (set point w). The positioner compares
the control signal of a control system to the
travel or rotational angle of the control valve
and issues a signal pressure (output vari-
able y) for the pneumatic actuator.
The positioner mainly consists of an electric
travel sensor system, an analog i/p convert-
er with a downstream air capacity booster
and the electronics with the microcontroller.
Serial
20
Interface
13
4
24V DC
17
12
8
Fig. 1: Functional diagram
EB 8384-5
16
mm
%
S
5
19
w
PD
x
18 3
6
9
Q 10
7

Design and principle of operation

When a system deviation occurs, the actua-
tor is either vented or filled with air. If neces-
sary, the signal pressure change can be
slowed down by a volume restriction. The
signal pressure supplied to the actuator can
be limited by software or on site to 1.4, 2.4
or 3.7 bar.
The fixed flow regulator ensures a constant
air flow to the atmosphere, which is used to
flush the inside of the positioner housing and
to optimize the air capacity booster. The i/p
converter is supplied with a constant up-
stream pressure by the pressure regulator to
compensate for any fluctuations in the supply
pressure.
15
14
2 11
G G
1
y
x
1 Control valve
2 Travel sensor
3 PD controller
4 A/D converter
BE2
5 Microcontroller
6 i/p converter
BE1
7 Air capacity booster
8 Pressure regulator
9 Flow regulator
10 Volume restriction
11* Inductive limit switch
12* Solenoid valve
13 IEC 61158-2 interface
module
14 Binary input BI1 (passive)
15* Binary input BI2 (active)
16 Display
17* Actuation of solenoid valve
18* Electrical insulation
19 D/A converter
20 Communication interface
* Options
11