Reference Manual
748384-C
September 2003
Rosemount Analytical Inc. A Division of Emerson Process Management Analyzer Variables
2-33
NGA2000 Reference
LIN_UNDER
Direction Bidirectional
Binding
None
Type
4-element floating point array
Value range
0 - 100; normally 5
Units Percent
Description
The amount less than the linearization range over which this curve is valid.
Usage
LIN_OVER.and LIN_UNDER shows how far negative the signal can go before the
input/output relationship becomes linear with slope equal to the slope at zero. It is
expressed in percent of the linearization range given by LINRNGHI.
See also
Other LINxxxxxxxx variables
LIN_UNITS
Direction Bidirectional
Binding
LIN_UNITS
Type Enumerated
Value range
Percent of span gas, ppm
Units None
Description
Allows the user to express the gas concentration as a percentage of the span gas or
as an absolute value in ppm
Usage
Allows the user to dilute a span gas, and therefore to avoid having to re-enter all 20
gas values when he changes his span gas
See also
LIN_VAR_ID
Direction Bidirectional
Binding
LIN_UNITS
Type Enumerated
Value range
Point 1 to Point 20
Units None
Description
Allows the user to specify which gas sample he is entering
Usage
Controls the self-linearization measurement.
See also
LINA0_
LINA1_, LINA2_, LINA3_, LINA4_
Direction Bidirectional
Binding
None
Type
4-element floating point array
Value range
Sum of each set of elements must be 1.0 ± 0.02.
Units None
Description
Linearizer coefficients. Each element applies to the range given by that element
number, so LINAO-1 is the zeroth coefficient for range 1.
Usage
NGA analyzers use a fourth order polynomial to linearize the normalized output of
the sensors. The input range to the polynomial covers 0 - 1, and the output should
cover that range as well. In general, the curve passes through the points (0,0) and
(1.0,1.0), within the limits of acceptable error, usually 2%, i.e. ± 0.02 to 1.0 ± 0.02.
These coefficients may be written to as desired, although Rosemount cannot
guarantee linearization specifications if locally produced values are used. It is
essential that the polynomial produced be monotonic over the range of 0 - 1,
otherwise the calibration routines may fail.
See also
Other LINxxxxxxxx variables