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3.0 Analogue Input Blocks
PR5350 has 2 Analogue Input Blocks to be configured individually. The constrcution of the
Blocks is in line with the standards from FOUNDATION Fieldbus and Profibus Nutzerorgan-
isation respectively, and producer specific parameters have not been added. However, the
Analogue Input Blocks for Fieldbus Foundation and Profibus are dissimilar due to the para-me-
ter differences.
3.1 Analogue Input Blocks, Fieldbus Foundation
3.2 Overview
The AI block takes the manufacturer’s input data, selected by channel number, and makes it
available to other function blocks at its output.
3.3 Analogue Input Block Schematic
3.4 Description
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 Ind Sqr 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. 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.
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. The PV filter, whose
time constant is PV_FTIME, is applied to the PV, and not the FIELD_VAL.
