ABB 2600T Series Instruction Manual page 81

2 6 0 0 T S E R I E S | P R E S S U R E T R A N S M I T T E R S | O I/ 2 6 6/ F F - E N R E V. E
Control Application Process (CAP) Blocks
Enhanced-Analog Input Function Block (E-AI)
Overview
The Analog Input receives in input variables produced in the Transducer Block via the selected CHANNEL. It is possible that some
transmitters have more Transducer Blocks or more variables produced within one Transducer Block. The CHANNEL setting allows
the user to select the desired variable to be used in input for the AI.
Block Diagram
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 cut-off" option in the IO_OPTS bit string. If the option bit is true, any
calculated output below the low cut-off 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.
Equations
The Analog Input receive in input the Transduce Block variable Value selected with the CHANNEL. The Input
Value is represented as CHANNEL Value in the following formula:
CHANNEL_VALUE XD_SCALE_0%
FIELD_VAL = 100 *
XD_SCALE_100% XD_SCALE_0%
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