5/12/2017
TECH-538/D.W.O. 23160
Page 66 of 189
Description of Functions
The functions available in the
Cofg
menu are described as follows:
Flow -
This function is used to set the flow characteristic of the positioner. Therefore, it’s possible to adjust the
“positioner-setpoint” to “actual-valve-position” ratio to compensate for non-linear valve flow characteristics.
This can be used so the “positioner-setpoint” will represent a closer approximation to the actual process flow.
The options are
Lin
(Linear)
,
EP
(Equal Percentage)
and
Opn
(Quick Opening)
. When Equal Percentage and Quick
Opening are used the setpoint and valve position will display a modified value, not the actual setpoint sent to the
ICoT. For instance, if “Quick Opening” is selected and a setpoint of 20% is sent to the ICoT, the local display will
show %SP 36.9 and when it reaches position (at 36.9% open), it will display %PS 36.9 (PS = position).
The
Lin
(Linear)
positioner characteristic duplicates the inherent characteristic of the valve and is the most often
used setting. (See next picture
Figure 8-21 – Valve flow characteristics
Type -
This function configures the positioner for the type of valve. The options are
Rot
(Rotary)
and
Lin
(Linear)
.
This setting needs to be done in order to configure the positioner to recognize the type of magnetic feedback being
given to the positioner. This setting is shown on the left side of the local display, where “R” indicates rotary type
and “L” indicates linear type.
Figure 8-22 – Valve Type shown on the left side of the local display
VALVE POSITION % OF TRAVEL
QUICK OPENING
80
60
40
20
0
0
20
40
60
80
100
100
EQUAL PERCENTAGE
LINEAR
VALVE FLOW CHARACTERISTICS
