Instruction Manual

748213-S April 2002

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 function of the span and range used, and can be computed for each individual case.

If the zero and span standard gases contain the same background gas as the sam- ple, the routine standardization procedure automatically compensates for the background components. Therefore, the zero and span standard gases would introduce no error.

If the background gas in the sample is different from that in the zero and/or span standard gas(es), background effects must be taken into consideration to ensure correct readout. During adjustment of the front panel ZERO and SPAN controls (see Figure 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 correct readout during subsequent analysis of the sample gas.

3-2

Operation

Rosemount Analytical Inc. A Division of Emerson Process Management