Rosemount 755A, Инструкция по эксплуатации

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I
NITIAL
S
TARTUP AND
C
ALIBRATION
245364-U Rosemount Analytical April 2000 3-7
Model 755A Oxygen Analyzer
When on-scale reading is obtained, allow analyzer to warm up for at least one hour
with gas flowing. This warm-up is necessary because a reliable calibration is
obtainable only after the analyzer reaches temperature stability. Moreover, the
resultant elevated temperature will ensure against condensation within, and possible
damage to the detector assembly.
After analyzer warm-up, the digital display or recorder should give stable, drift-free
readout; if so, proceed to Section 3.3. Otherwise refer to Section 7, Routine Service
and Maintenance.
3.3 CALIBRATION
Calibration for oxygen readout consists of establishing a downscale and upscale point.
3.3.1 C
ALIBRATION
U
SING
D
IGITAL
R
EADOUT FOR
O
XYGEN
R
EADOUT
The digital display covers the full range of 0.00% to 100.005 oxygen and thus will
normally be used as the readout device during calibration. If so, almost any down-
scale and upscale standards may be used. Typically the downscale standard will be
an oxygen-free gas such as nitrogen, and the upscale standard will be some readily
obtained gas such as dry air (20.93% oxygen) or 100% oxygen. Purity requirements
will be dictated by the accuracy requirements of the application.
3.3.2 C
ALIBRATION
U
SING
R
ECORDER FOR
O
XYGEN
R
EADOUT
In some applications the recorder readout may be the important display and may thus
be used during calibration. If so, the down-scale standard gas is selected to establish
a calibration point at or near the lower range-limit of the selected range:
1. A zero-based range normally uses an oxygen-free gas, typically nitrogen.
2. A zero-suppressed range uses a blend consisting of a suitable percentage of
oxygen contained in a background gas, typically nitrogen.
The upscale standard gas is required to establish a calibration point at or near the
upper range limit. For example, if this range limit is 21% (or somewhat greater than
21%), the usual upscale standard gas is dry air (20.93% oxygen).
Typical examples of standard gases for recorder oxygen ranges are shown in Table 3-
2.