Samson 4763, Mounting And Operating Instructions

With a 4 to 20 mA input signal, for exam-

ple, the valve must also move through the

entire range (0 to 100 % ). The starting point

then is 4 mA and the upper range value

20 mA.
In split-range operation, the controller output

signal used to control two control valves is

divided in such a way that these valves

move through their entire travel with half of

the input signal range (e.g. first valve set to

4 to 12 mA, second valve set to 12 to

20 mA). To prevent the two from overlap-

ping, a dead band of ±0.5 mA as in Fig. 13

must be taken into account.
The starting point (zero) is adjusted using

the zero adjustment screw (4), the reference

variable span and, hence, the upper range

value using the pin (2).

4.3 Setting the positioner at the

valve

4

Connect an ammeter to the control signal

input at the terminals 11 (+) and 12 (–).

4

Connect the supply air to the supply input

(supply 9).

4.3.1 Setting the air delivery

(volume restriction Q) and

proportional band XP

1. Close the volume restriction (14) as far

as the required speed of response al-

lows.

You can check the speed of response by

pressing the range spring (6) as far as it

will go.

2. Set the input signal to approximately 50

% of its range. Then, turn the zero adjust-

ment screw (4) until the valve is at ap-

proximately 50 % valve travel.

On setting the Xp restriction, observe the re-

lationship with the supply air pressure as in-

dicated in Fig. 14. The preset value of Xp

should read approximately 3 %.
3. Check the plug stem's tendency to oscil-

lation by pressing the range spring (6)

briefly as far as it will go.

Xp should be set to a value as small as

possible, however, without causing no-

ticeable overshoot.

Note:

Always determine the Xp setting prior to ad-

justing the starting point. Subsequent modifi-

cation displaces the zero point!

The zero can also be shifted by altering the

adjusted supply air pressure.

If necessary, check the zero adjustment un-

der operating conditions of the plant and,

re-adjust, if need be.

EB 8359-2 EN

15

Operation

Zul.  Supply   Alim.

Xp

[%]

5
4
3
2
1
0

6 bar 3 bar 1.4 bar

90°

0°

180° 270°

270°

90°

180°

0°

360°

Fig. 14 · Setting the XP restriction