Air Output Capacity And Proportional Band - Samson 3767 Translation Of Original Instructions

Installation
positioner (>> or <>), this starting point
can be either the lower or upper range
value (4 or 20 mA) of the set point.
− The set point range and thus the upper
range value determine the travel of the
valve.
− In split-range operation (Fig. 5-11, be-
low), the control valves work with smaller
set point ranges. The controller output
signal is used to control two control
valves, dividing it such that the valves
move through their entire travel range at
half the input signal range each (e.g. first
valve set to 4 to 12 mA, second valve set
to 12 to 20 mA). To avoid overlapping,
allow for a dead band of ± 0.5 mA as
shown in Fig. 5-11.
− The starting point (zero) is adjusted at
the zero adjuster (6.2); the span, i.e. the
upper range value, is adjusted at the
span adjuster (6.1).
− When the positioner is controlled by a
computer whose signal is limited, e.g.
between 4 to 20 mA, set the positioner
to the range from 4.5 to 20 mA. This is
the only way to ensure that the actuator
is completely vented and the valve com-
pletely closed when the controller issues
a 4 mA signal.
For operating direction <>, set the range
to 4 to 19.5 mA.
5-20
100%
100%
Open
Travel
Closed
0%
4
0%
4
100%
100%
< >
Open
Travel
Closed
0%
Valve 2
0% 4
4
Dead band
Fig. 5-11: Normal or split-range operation
Î Connect an ammeter to the control signal
input at the terminals 11 (+) and 12 (–).
Î Connect the supply air to the supply in-
put (supply 9).
5.5.1 Air output capacity and
proportional band X
1. Close the volume restriction (11 in
Fig. 5-3) as far as the required position-
ing speed permits.
< > < <
< > < <
20 mA
20 mA
Set point (input
signal)
< > < <
< <
Valve 1
12 20 mA
12 20 mA
P
EB 8355-2 EN