National Instruments NI-FBUS - Manual (Page 69)

Chapter 4 Parameters
NI-FBUS Configurator User Manual 4-4 ni.com
Figure 4-1. AI Scaling Procedure
XD_SCALE OUT_SCALE
Range:
What it Does:
Sample Settings:
XD_SCALE 0 to 100%
FIELD_VAL
Dependent on L_TYPE and OUT_SCALE
OUT
The transducer
in the device
produces some
physical signal
such as Volts,
Amps, etc. XD_SCALE specifies the
transducer scaling (field
range) of the physical
signal. From this information,
the physical signal value is
converted to a percentage
of the field range.
OUT_SCALE specifies the scaling
from FIELD_VAL (% of scale) to
output units. It is used in conjunction
with L_TYPE. The type of output
scaling is specified by L_TYPE.
The options are no scaling (direct),
linear scaling (indirect), or square
root scaling (indirect square root).
For example, if the physical
signal can range from –50 mV
to +50 mV, you would enter
the following:
Transducer Value
For example, if –50 mV at the
transducer corresponds to a
physical temperature of –100
°C,
+50 mV corresponds to 400 °C,
and the scaling should be linear,
you would enter the following:
XD_SCALE
EU_100
EU_0
UNITS_INDEX
DECIMAL
50
–50
mV
3
_
OUT_SCALE
EU_100
EU_0
UNITS_INDEX
DECIMAL
400
–100
°C
3
_
L_TYPE Indirect
Calculations:
FIELD_VAL =
(transducer_value – XD_SCALE.EU0)
XD_SCALE.EU100 – XD_SCALE.EU0
OUT Direct = transducer_value
FIELD_VAL
100
OUT Indirect = * (OUT_SCALE.EU100 – OUT_SCALE.EU0) + OUT_SCALE.EU0
OUT Indirect Square Root
= * (OUT_SCALE.EU100 – OUT_SCALE.EU0) + OUT_SCALE.EU0
FIELD_VAL
100