Page 48 FOUNDATION Fieldbus ST 700 Pressure Transmitter User's Guide Revision 2.0
XD_SCALE Range
In the AI block, XD_SCALE values are used when L_TYPE is set to Indirect which
converts the signal to other units. The high and low scale values of XD_SCALE (EU_100
and EU_0) define the range over which the AI OUT shows the status as Good.
• When L_TYPE is set to either Indirect or Direct, XD_SCALE units must match the
transducer units.
• When L_TYPE is set to Direct, it is recommended that XD_SCALE and
OUT_SCALE must contain the same values.
PV Value
The AI block PV value is determined based on the selected transducer channel’s
PRIMARY_VALUE.
AI OUT
AI in Manual Mode
When the AI block is in manual mode, OUT can be written as a fixed value between -10%
and +110% of the OUT_SCALE range. OUT values between 0 and 100% shows a status
of Good. OUT values outside the range shows a status of Uncertain. The “limit” field is
marked as Constant for all values. PV shows the live pressure signal in manual mode.
AI in AUTO Mode
L_TYPE determines whether the signal is taken directly from the transducer block and
passed to the AI block output (L_TYPE = Direct) or converted into different units before it
is passed to the AI block output (L_TYPE = Indirect or Ind Sqr Root). OUT_SCALE
determines the units’ conversion of the signal presented to the output.
• When L_TYPE is Direct, OUT is the same as the value passed from the transducer
block.
• When L_TYPE is Indirect, the PRIMARY_VALUE is converted to XD_SCALE and
that value is set equal to OUT (FIELD_VAL = %). The OUT in % is re-ranged to a
value using the OUT_SCALE.
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