Table of Contents
Advertisement
Instruction Manual
760000-C
November 2002
Choose the point to be measured from
the "Point to be measured" line.
At each point in succession, flow the gas
of the correct value and, when the reading
is stable, press the DATA (F3) softkey to
record the gas value and raw reading for
each point.
Move to the next two points with the
NEXT (F4) softkey and move backwards
with the ESCAPE (F2) softkey. After the
desired number of points has been meas-
ured and recorded, press ESCAPE from
the Point 1 menu to return to the "Poly-
nomial set up" menu.
In the "Polynomial set up" menu, press
the "CALC" softkey.
The analyzer will calculate the best fit
polynomial and store it as the coefficients
in the current range's linearizer function.
The order or the polynomial is optimized
based on the number of data points pro-
vided. At least 7 points are required for a
fourth-order polynomial correction. The
results can be modified with the "Midpoint
correction" also provided. See Section 3-
7e, page 3-15.
The linearization curve must be mono-
tonic. If it is not, the calibration routine
will fail and the analyzer will not cali-
brate. Test this by copying the values
of the linearization coefficients into a
spreadsheet program and plotting the
results.
The analyzer does not test for monotonic-
ity when it spans, but this test may not
catch all possible errors.
Monotonic means that the curve does not
change direction as the gas concentration
increases.
3-16
Operation
CAUTION.
Midpoint Correction Set Up
This function allows the adjustment of the
primary variable output into a precise
value using up to three midpoints. It does
this with a piecewise-linear algorithm that
occurs after and in addition to any poly-
nomial linearization. .
The correction can be performed indi-
vidually for each range.
CLD
Correction:
Point being mesured:
Point 1 gas concentration:
Point 2 gs concentration:
Point 3 gas concentration:
Point 1 reading:
Point 2 reading:
Point 3 reading:
Span gas value:
Analyzer function:
HOME
First, disable the correction.
Set the point being measured to Point 1.
Then enter the first midpoint gas value,
run the gas, and when stable, press
"SET." "Point 1 reading" will show the ac-
tual reading, but the analyzer will adjust it
to the correct value.
Repeat the above steps with the second
and third points as desired.
When complete, se the "Correction:" line
to "ENABLED" to activate the correction.
Rosemount Analytical Inc.
A Division of Emerson Process Management
Model NGA2000 CLD
Main Menu
↓
Analyzer and I/O expert controls &
setup...
↓
Analyzer module setup...
↓
Gas measurement parameters...
↓
Linearization functions...
↓
Midpoint correction set up...
Midpoint correction setup
Point 1
ESCAPE
SET
Figure 3-22. Midpoint Correction
Setup Menu
7.50 ppm
DISABLED
Point 1
2.50 ppm
5.00 ppm
7.50 ppm
2.52 ppm
5.12 ppm
7.56 ppm
10.00 ppm
READY
RANGE 2
INFO
Advertisement
Table of Contents
