Basic Instructions; Advanced Instructions; Troubleshooting; Spanning - Emerson NGA2000 Reference Manual

Reference Manual
748384-C
September 2003
1-7

SPANNING

Spanning is the function of adjusting an ana-
lyzer's measurement gain such that a near
fullscale gas reads correctly. Since this reading
depends on the zero, it is essential that you per-
form a zero before a span. It is also essential
that you verify that the span gas value has been
entered correctly in the calibration gas screens.
Linearization is the function of making sure that
the readings in between the zero and span point
also read correctly. See the section below for
this.
a.

Basic instructions

Set Span Gas Concentrations
Get into the Main menu.
Select Expert controls and setup
Select Analyzer module setup.
Select Calibration gas list..
Change any zero or span gas concentra-
tions as desired. (Span gas values must be
within 20 - 120% of the range fullscale.)
Perform A Span
Get into the Main menu.
Flow the appropriate span gas through the
analyzer.
Select Basic controls...
Verify sample gas flow.
Press "SPAN", then "SPAN" again.
Press the left arrow or "HOME" when you
are done.
b.

Advanced instructions

As per basic controls, except do the span
through the Expert controls and setup
menu.
Enter the Main menu.
1-16 Introduction
NGA2000 Reference
Flow the appropriate span gas through the
analyzer.
Select Expert controls and setup
Select Expert controls...
Verify sample gas flow.
Press "SPAN", then "SPAN" again.
Press the left arrow key, then press Re-
sults...
Examine this screen for data about the most
recent calibration.
Press the left arrow or "HOME" when you
are done.
c. Details
Spanning is less critical than zeroing. The
analyzer will take several time constants to
get to a good span value, so verify its signal
is really stable before spanning.
Most span problems are due to the use of
an incorrect span gas, or an incorrect span
gas setting.
Network variables: CALTIME, CALTME-
OUT, ZERO, SPAN, AMFN, CALCHKLIM-
ITS, ZERORNGS, CALRANGES,
CALFAIL, CALFPC
d.

Troubleshooting

After a span, zero reads OK but the span
gas doesn't read right...
You may not have left the span gas in long
enough to get a stable span. Put the span
gas back into the analyzer, and watch the
trend of its reading on a chart recorder or
computer screen. The reading should be
stable when you do a span. If it is still
trending upwards, you have not spanned on
the real span gas. Either leave it to stabilize
more, or troubleshoot your sample system
until you get a good span gas stability. For
example, entrained condensate in the sys-
tem will affect the span stability. So will the
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