Rosemount 755, Instruction Manual

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1
I
NTRODUCTION
748183-H
1-1
Rosemount Analytical
November 1997
The Model 755 Oxygen Analyzer provides continuous read-out of the oxygen content
of a flowing gas sample. The determination is based on measurement of the magnetic
susceptibility of the sample gas. Oxygen is strongly paramagnetic, other common
gases are weakly diamagnetic, with few exceptions.
The instrument provides direct read-out of oxygen concentration on a front-panel
meter. In addition a field-selectable voltage output is provided as standard. An isolated
current output of 4 to 20 mA or 0 to 20 mA is obtainable through plug-in of the optional
circuit board. Current and voltage outputs may be utilized simultaneously, if desired.
The basic electronic circuitry is incorporated into two master boards designated the
Control Board and the Case Board, see Figure 1-2. The Control Board has
receptacles that accept optional plug-in circuit boards thus permitting inclusion of such
features as current output and alarms, and facilitating conversion from one range
option to another.
The analyzer is available in a general purpose enclosure or an explosion proof
enclosure. See Figures 1-1.
1.1 RANGE OPTIONS
The Model 755 is supplied, as ordered, with four switch-selectable ranges: an overall
range and three sub-ranges, each covering a portion of the overall range. The
standard range options are of two general types: zero-based (Section 1.1.1) and zero-
suppressed (Section 1.1.2). In addition, special range options incorporating
combinations of zero-based and zero-suppressed ranges are available on factory
special order, refer to Section 1.1.3. All range options utilize a front-panel meter with
left-hand zero. See Figure 1-1 and Table 1-1.
1.1.1 S
TANDARD
Z
ERO
-B
ASED
R
ANGE
O
PTIONS
In a zero-based range option, the lower range-limit for all four ranges is 0% oxygen.
There are five standard zero-based range options:
•
Range Option
•
Sub-Range A
•
Sub-Range B
•
Sub-Range C
•
Overall Range
Refer to Table 1-2.