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Instruction Manual
245364-V
May 2002
Rosemount Analytical Inc. A Division of Emerson Process Management Installation 2-7
Model 755A
2-5 CALIBRATION GASES
a. Zero Calibration Gas
Zero-based range - Normally uses a
oxygen-free gas, typically nitrogen.
Zero-suppressed range - Uses a blend
consisting of a suitable percentage of
oxygen contained in a background gas,
typically nitrogen.
b. Downscale Standard Gas
Digital Display - Typically, although not
necessarily, the downscale standard gas
will be oxygen-free, such as nitrogen.
Recorder Readout - The downscale
standard gas is selected to establish a
calibration point at or near the lower
range limit.
c. Upscale Standard Gas
Digital Display - Typically, the upscale
standard gas will be a readily obtained
gas such as dry air (20.93% oxygen) or
1005 oxygen.
Recorder Readout - A suitable upscale
standard gas is required to establish a
calibration point at or near the upper
range limit. If this range limit is 21% or
somewhat above 21%, the usual standard
gas is dry air (20.93% oxygen).
2-6 SAMPLE HANDLING
CAUTION
PRESSURE LIMIT
Under no circumstances allow pressure to
exceed 10 psig (69 kPa) as irreparable
damage to the detector may result.
Many different sample handling systems are
available, depending on the requirements of
the individual user. Most sample handling
systems have copper or brass components;
however, stainless steel components are
available for applications involving corrosive
gases. With corrosive gases, complete drying
of the sample is desirable, as most of these
gases are practically inert when totally dry.
For specific corrosive applications, consult the
factory.
a. Sample Temperature Requirements
Sample temperature at the analyzer inlet
should be in the range of 50°V to 150°F
(10°C to 66°C). With a thoroughly dry
sample, entry temperature can be as high
as 150°F (66°C) without affecting readout
accuracy. Normally, a maximum entry
temperature of 110°F (43°C) is
recommended so that the sample
temperature will rise during passage of
the sample through the analyzer. This
precaution ensures against cooling of the
sample and possible condensation of
moisture. Such condensation should be
avoided as it may damage the detector.
b. Sample Pressure Requirements:
General
Operating pressure limits are the
following: maximum, 10 psig (69 kPa
gauge pressure); minimum, -1.9 psig (-
13.1 kPa).
CAUTION
OPERATING LIMITS
Operation outside the specified limits may
damage the detector and will void the
warranty.
Oxygen readout is automatically corrected
for atmospheric pressure variations within
±3% of the target value, which may be set
anywhere within the range of -2.7 to 3.3
psig ±3 psig (-18.6 to 22.8 kPa ±21 kPa).
The basic rule for pressure of sample and
standard gases supplied to the inlet is to
calibrate the analyzer at the same
pressure that will be used during
subsequent operation and to maintain this