Emerson Rosemount 5900C, Справочное руководство

Страница: 168 / 322

4.11.11 Signal conversion
You can set the signal conversion type with the Linearization Type (L_TYPE) parameter.
You can view the converted signal (in percent of XD_SCALE) through the FIELD_VAL
parameter.
You can choose from direct or indirect signal conversion with the L_TYPE parameter.
FIELD_VAL = 100 × Channel Value − EU*@0%
EU*@100% − EU*@0%
* XD_SCALE values
Direct
Direct signal conversion allows the signal to pass through the accessed channel input
value (or the simulated value when simulation is enabled).
PV = Channel Value
Indirect
Indirect signal conversion converts the signal linearly to the accessed channel input value
(or the simulated value when simulation is enabled) from its specified range (XD_SCALE)
to the range and units of the PV and OUT parameters (OUT_SCALE).
PV = FIELD_VAL
100
× EU**@100% − EU**@0% + EU**@0%
** OUT_SCALE values
Indirect square root
Indirect Square Root signal conversion takes the square root of the value computed with
the indirect signal conversion and scales it to the range and units of the PV and OUT
parameters.
PV =
FIELD_VAL
100
× EU**@100% − EU**@0% + EU**@0%
** OUT_SCALE values
When the converted input value is below the limit specified by the LOW_CUT parameter,
and the Low Cutoff I/O option (IO_OPTS) is enabled (True), a value of zero is used for the
converted value (PV). This option is useful to eliminate false readings when the differential
pressure measurement is close to zero, and it may also be useful with zero-based
measurement devices such as flowmeters.
Note
Low Cutoff is the only I/O option supported by the AI block. You can set the I/O option in
Manual or Out of Service mode only.
Configuration Reference Manual
September 2019 00809-0100-5901
168 Reference Manual