Samson 3767, Mounting And Operating Instructions

Page: 39 / 68

EB 8355-2 EN 39
Operation
100%
0%
4 20 mA 12
4
20 mA
100%
0%
< > < < < > < <
Reference variable
Input signal
Dead band
Open Open
Travel Travel
Closed Closed
Valve 2 Valve 1
Fig. 13: Normal or split-range operation
5.1.1 Adjusting the proportional
band Xp and air delivery
Q
1. Close the volume restriction (11) as far
as the required positioning speed
permits.
Check the positioning speed by pushing
the diaphragm lever (3) as far it will go.
2. Adjust the reference variable at the input
to approx. 50 % of its range.
3. Turn the zero adjuster (6.2) until the
valve has reached approx. mid-travel.
4. Use the adjuster (8) to set the proportion-
al band X
p
to a value half way (half
turn).
5. Check the valve's tendency to hunt and
the positioning speed by briefly tapping
the diaphragm lever (3).
The X
p
value is to be adjusted to be as
small as possible, without considerable
overshooting occurring.
NOTICE
Always adjust the X
p
restriction be-
fore setting the starting point.
Changing it later will cause the zero
point to be shifted.