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

Design and principle of operation

3 Design
operation
The electropneumatic positioner is attached
to pneumatic control valves. It is used to as-
sign the valve stem position (controlled vari-
able x) to the control signal (reference vari-
able w). The input signal received from a
control system is compared to the travel or
rotational angle of the control valve, and a
pneumatic signal pressure (output variable
y) is produced.
The positioner consists of a travel sensor sys-
tem proportional to resistance, an analog
i/p converter with a downstream booster
and the electronics unit with microcontroller.
Serial
20
Interface
13
F
OUNDATION
fieldbus
4
IEC 61158-2
24V DC
17
12
8
Fig. 2 · Functional diagram
12
EB 8384-5 EN
and principle
16
mm
%
S
5
19
w
PD
x
3
18
6
9
Q 10
7
When a deviation occurs, the actuator is
of
pressurized or vented. If required, the
changes in the signal pressure can be
slowed down by a connectable Q restric-
tion. The signal pressure supplied to the ac-
tuator can be limited by software or on site
to 1.4, 2.4 or 3.7 bar.
A constant air stream to the atmosphere is
created by the flow regulator (9) with a
fixed set point. The air stream is used to
purge the inside of the case as well as to op-
timize the air capacity booster. The i/p
module (6) is supplied with a constant up-
stream pressure by the pressure regulator
(8) to make it independent of the supply air
pressure.
15
14
11
2
G G
1
y
x
1 Control valve
2 Travel sensor
3 PD controller
4 A/D converter
5 Microcontroller
BE2
6 i/p converter
7 Air capacity booster
BE1
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, passive
15* Binary input, active
16 Display
17* Solenoid valve control
18* Galvanic isolation
19 D/A converter
20 Communication interface
* Optional