Pepperl+Fuchs FD0-VC-Ex4.FF Manual page 32

"PV_D generation"
If one of the options A to D was selected under "Sensor usage", "PV_D generation" can be used to deter-
mine whether and how to further treat the evaluated signals prior to transferring them to the function block.
The following options can be selected:
• Valve Position
• Valve Position Extended
• Intermediate => Closed
• Intermediate => Open
• Intermediate => Next
• Intermediate => Last (default)
Valve Position:
The position of the valve is transferred to the function block as a numerical value:
Numerical value
1
2
3
0
Valve Position Extended:
The information about the valve position is extended in the intermediate position by the information "opens"
and "closes". This information is determined from the current control process and need not coincide with the
actual direction of travel (e. g. when changing the set position while the valve is in the intermediate position).
Numerical value
1
2
3
4
0
The two options "Valve Position" and "Valve Position Extended" as well as the setting "Use sensor values
for PV_D" in Sensor usage generate a problem for the function block:
As shown in section 6.3, the valve position transferred from the transducer block to the function block is
given in the parameter READBACK_D. From there it is transferred to the Parameter PV_D which (via
BKCAL_OUT_D) can be transferred to a control system in cycles or used in a function block application.
If an inversion is active in the function block, the numerical value "0" becomes "1" and all numerical values
unequal to zero become "0". I. e. all valid valve positions are inverted to "0".
Also the IO options of the DO function block "SP-PV Track in LO" and "SP-PV Track in Man" are no longer
functioning because the range of values of PV_D does not correspond to that of SP_D.
To solve these problems and to allow a more simple use of the valve position in the function block applica-
tion, the valve position can be shown at the range of values of the set position ["closed" (0) or "open" (1) ]
by means of the four remaining options. These four options determine which position shall be output in the
intermediate position:
Intermediate => Closed
Intermediate => Open
Intermediate => Next
Intermediate => Last
(default setting)
Subject to reasonable modifications due to technical advances.
32
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Parameterisation and operation of the valve coupler
Valve position
Closed
Open
Intermediate position
Unknown
Valve position
Closed
Open
Intermediate position/opening
Intermediate position/closing
Unknown
The intermediate position is always interpreted as "closed"
The intermediate position is always interpreted as "open"
During a closing process, the intermediate position is always inter-
preted as "closed" and during an opening process as "open"
During a closing process, the intermediate position is interpreted as
"open" and during an opening process as "closed"
Fieldbus Valve Coupler FD0-VC-Ex4.FF
Copyright Pepperl+Fuchs, Printed in Germany