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Instruction Manual
245364-V
May 2002
Rosemount Analytical Inc. A Division of Emerson Process Management Operation 3-1
Model 755A
SECTION 3
OPERATION
3-1 OVERVIEW
Preparatory to startup and calibration, the
operator should study Figure 3-1 (page 3-2),
Figure 3-2 (page 3-7) and Table 3-1 (page 3-
5). Together they give locations and
summarized descriptions of operating controls
and adjustments of the Model 755A.
3-2 SELECTION OF RECORDER OXYGEN
RANGE
The digital display provides readout over the
full range of 0.00% to 100.00% oxygen,
eliminating the requirement for expanded-
scale operation. With a recorder, however,
resolution is normally limited to approximately
1% of fullscale. Thus, if the recorder output is
to be the important display medium for the
particular application, expanded-scale
operation may be necessary to obtain the
desired readout accuracy. Such operation is
obtained by an appropriate combination of
scale expansion and zero suppression.
a. Recorder Oxygen Range Selection
Procedure
Refer to Table 3-1 (page 3-5) and Figure
3-2 (page 3-7).
1. Verify that Recorder Voltage Output
Jumper is in the position appropriate
to the recorder: 10 mV, 100 mV, 1 V
or 5 VDC.
2. Place the Recorder Oxygen Span
Jumper in the position appropriate to
the desired span. Note that on the
circuit board switch positions are
marked according to the amplifier
gain.
Desired Oxygen
Span for Recorder
Amplifier Gain
Marking on Board
100% 1X
20% 5X
10% 10X
5% 20X
2% 50X
1% 100X
3. Select the required zero suppression
by appropriate settings of the
following:
a. Set Recorder Zero Suppression
Jumper for fixed value of 0%,
20%, 40%, 60% or 80% oxygen.
b. Set Recorder Zero Suppression
Coarse Adjustment R41 for
appropriate value in the range of
05 to 25% oxygen.
NOTE:
The actual applied zero suppression
may be measured and established via
readout on the digital display per the
procedure of Section 3-2b (page 3-3).
Example 1, Selection of a Zero-Based
Recorder Output Range:
•
Desired oxygen range for recorder
output: 0 to 100%.
•
Required span of 100% oxygen is
selected when Recorder Oxygen
Span Jumper is in the 1X position.
•
Required Zero Suppression is 0%,
thus Recorder Zero Suppression
Jumper, is removed, and R41,
Recorder Zero Suppression Coarse
Adjustment, and R104, Recorder Zero
Suppression Fine Adjustment, are
adjusted for 0% oxygen.