Emerson 755A - Manual (Page 37)

Instruction Manual
245364-V
May 2002
Rosemount Analytical Inc. A Division of Emerson Process Management Operation 3-5
Model 755A
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, page 3-6.
A. TYPICAL ZERO-BASED RANGES
0 to 1 Nitrogen 0.9% O2 Balance N2
0 to 10 Nitrogen 9% O2 Balance N2
0 to 100 Nitrogen 100% O2
B. TYPICAL ZERO-SUPPRESSED RANGES
RANGE
% O2
RECOMMENDED STANDARD GAS
RECOMMENDED UPSCALE
STANDARD GAS
20 to 21 20.2% ±0.2% O2 Air (20.93% O2)
11 to 21 11.2% ±0.2% O2 Balance N2 Air (20.93% O2)
99 to 100 High Purity O2 with 0.8% ±0.05% High Purity N2 High Purity O2
90 to 100 91% ±0.5% O2 Balance N2 High Purity O2
Table 3-1. Standard Gases Recommended for Calibration of Various Oxygen Ranges on Analog Output