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Reference Manual
00809-0200-4101, Rev AA
July 2008
3-5
Rosemount 2051
ANALOG INPUT (AI)
FUNCTION BLOCK
Configure the AI block
A minimum of four parameters are required to configure the AI Block. The
parameters are described below with example configurations shown at the
end of this section.
CHANNEL
Select the channel that corresponds to the desired sensor measurement. The
2051 measures both pressure (channel 1) and sensor temperature (channel
2).
L_TYPE
The L_TYPE parameter defines the relationship of the sensor measurement
(pressure or sensor temperature) to the desired output of the AI Block (e.g.
pressure, level, flow, etc.). The relationship can be direct, indirect, or indirect
square root.
Direct
Select direct when the desired output will be the same as the sensor
measurement (pressure or sensor temperature).
Indirect
Select indirect when the desired output is a calculated measurement
based on the sensor measurement (e.g. a pressure measurement is made
to determine level in a tank). The relationship between the sensor
measurement and the calculated measurement will be linear.
Indirect Square Root
Select indirect square root when the desired output is an inferred
measurement based on the sensor measurement and the relationship
between the sensor measurement and the inferred measurement is
square root (e.g. flow).
XD_SCALE and OUT_SCALE
The XD_SCALE and OUT_SCALE each include three parameters: 0%,
100%, and, engineering units. Set these based on the L_TYPE:
L_TYPE is Direct
When the desired output is the measured variable, set the XD_SCALE to
the “Primary_Value_Range”. This is found in the Sensor Transducer Block.
Set OUT_SCALE to match XD_SCALE.
L_TYPE is Indirect
When an inferred measurement is made based on the sensor
measurement, set the XD_SCALE to represent the operating range that
the sensor will see in the process. Determine the inferred measurement
values that correspond to the XD_SCALE 0 and 100% points and set
these for the OUT_SCALE.
Table 3-1. I/O Channel Definitions
Channel Number Channel Description
1 differential pressure in AI.XD_SCALE units
2 sensor temperature in AI.XD_SCALE units