Analog Input Block; Execution; Figure 6: Analog Input Block - Honeywell ST700 User Manual

3.8

Analog Input block

The Analog Input (AI) block takes the transducer's input data, selected by channel number,
and makes it available to other function blocks at its output. The variables to be used by the
block are defined through the available channels: DP/AP/GP, Electronic Housing
Temperature, Fluid Flow, Fluid Level, Meterbody Temperature, and Static Pressure.

Execution

Transmitter Output Signal and Status
Viewing certain parameters and their values and status in the transmitter and understanding
their relationship to each other is helpful in understanding transmitter output signal and
status. The following paragraphs and tables describe transducer and AI block parameters
which directly determine the way the transmitter output is presented.
Pressure Sensor Signal
In Transducer block, the pressure signal is represented as PRIMARY_VALUE. This
pressure signal uses the elements in PRIMARY_VALUE_RANGE to determine the
engineering units, the decimal places for the display and also the high and low scale of the
value. This pressure signal becomes the PV value in the AI block, and uses the elements of
OUT_SCALE in determining the units, decimal places and also the high and low scale
values of PV. The pressure signal leaves the AI block as OUT value, which also uses the
elements of OUT_SCALE.
The Transducer scaling (XD_SCALE) is applied to the value from the channel to produce
the FIELD_VAL in percent. The XD_SCALE unit's code must match the channel unit's
code or be supported by the device, if this is not the case the block remains in OOS mode,
after being configured.
Page 46 FOUNDATION Fieldbus ST 700 Pressure Transmitter User's Guide

Figure 6: Analog Input Block

Revision 2.0