Instruction Manual

Instruction Manual
748213-S
April 2002
3-2 Operation Rosemount Analytical Inc. A Division of Emerson Process Management
Model 755R
Set Span Calibration Point
Inject span standard gas (see Table
3-1, page 3-4) through the analyzer at
the same flow rate as was used for
zero standard gas. Allow gas to purge
analyzer for a minimum of three min-
utes.
Adjust SPAN control so that reading on
display or recorder is appropriate to the
span standard gas.
3-5 COMPENSATION FOR COMPOSITION OF
BACKGROUND GAS
Any gas having a composition other than
100% oxygen contains background gas.
The background gas comprises all non-
oxygen constituents. Although instrument
response to most gases other than oxygen
is comparatively slight, it is not in all cases
negligible. The contribution of these com-
ponents to instrument response is a func-
tion of the span and range used, and can
be computed for each individual case.
If the zero and span standard gases con-
tain the same background gas as the sam-
ple, the routine standardization procedure
automatically compensates for the back-
ground components. Therefore, the zero
and span standard gases would introduce
no error.
If the background gas in the sample is dif-
ferent from that in the zero and/or span
standard gas(es), background effects must
be taken into consideration to ensure cor-
rect readout. During adjustment of the front
panel ZERO and SPAN controls (see Fig-
ure 1-1, page 1-1), the instrument is not set
to indicate the true oxygen content of the
zero and span standard gases. It is set to
indicate a slightly different value, relative to
background gas, calculated to provide cor-
rect readout during subsequent analysis of
the sample gas.