Flowserve MX FOUNDATION Fieldbus Field Unit - Manual (Page 29)

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MX/QX FOUNdaTION Fieldbus Field Unit FCd LMENIM2330-01 – 08/11
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measurement. The measuring device may have several measurements or derived values available in
different channels. Use the Channel number to define the desired variable from the transducer block.
There is one AI block in the Limitorque actuator control system, and two channels:
Channel No.12 — AI_POSITION_CHAN — Current valve position
Channel No.13 — AI_ANALOG_INPUT_1_CHAN — Value of analog input 1
Figure 3.2 – Analog Input Block
The AI block supports alarming, signal scaling, signal filtering, signal status calculation, mode
control, and simulation. In Automatic mode, the block’s output reflects the Process Variable (PV)
Value and Status. In Manual Mode, Output may be set manually by the operator. Manual Mode is
reflected on the Output Status. Alarms can be generated based on the value of the block output.
Output
OUT is the block output value and status.
Scaling
Transducer scaling (XD_SCALE) is applied to the value from the channel to produce the FIELD_VAL
in percent. The XD_SCALE units code must match the channel units code (if one exists), or the block
will remain in O/S mode after being configured. A block alarm for units mismatch will be generated.
The OUT_SCALE is normally the same as the transducer, but if L_TYPE is set to Indirect or Indirect
Square Root, OUT_SCALE determines the conversion from FIELD_VAL to the output. PV and OUT
always have identical scaling.
OUT_SCALE provides scaling for PV. The PV is always the value that the block will place in OUT if the
mode is Auto.
Manual Mode
If Man is allowed, someone may write a value to the output. The status will prevent any attempt at
closed loop control using the Man value, by setting the Limit value to Constant.
Low Cutoff
The LOW_CUT parameter has a corresponding “Low cutoff” option in the IO_OPTS bit string. If the
option bit is true, any calculated output below the low cutoff value will be changed to zero. This is
only useful for zero based measurement devices, such as flow.
Output
Alarms
HI/LO
OUT
(to network)
Simulate
SIMULATE
Analog
measurement
AnaIog Input Block
Filter
PV_FTIME
PV
Convert
L_TYPE
XD_SCALE
OUT_SCALE
Cutoff
LOW_CUT
Mode
FIELD_VAL
(from actuator)