Figure 13: Analog Input Block Schematic Diagram - Honeywell SLG 700 Option Manual

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 block places the value in
OUT if the mode is AUTO. If MAN mode is allowed, write a value to the output. The status prevents
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 set as True, any calculated output below the low cut-off value changes 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
FIELD_VAL = 100*(channel value - EU@0%) / (EU@100% - EU@0%) [XD_SCALE]
Direct: PV = channel value
Indirect: PV = (FIELD_VAL/100) * (EU@100% - EU@0%) + EU@0% [OUT_SCALE]
Ind Sqr Root: PV = sqrt (FIELD_VAL/100) * (EU@100% - EU@0%) + EU@0% [OUT_SCALE]
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.
Rev.5

Figure 13: Analog Input Block Schematic Diagram

FOUNDATION Fieldbus Option User's Manual Page 71