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Instruction Manual
245364-V
May 2002
3-8 Operation Rosemount Analytical Inc. A Division of Emerson Process Management
Model 755A
c. Calibration with Downscale and
Upscale Standard Gases
1. Set downscale calibration point as
follows:
a. Set TEST switch (on analyzer
door) to NORM.
b. Pass downscale standard gas
through analyzer at suitable flow
rate, preferably 250 cc/min.
Allow gas to purge analyzer for
minimum of 3 minutes.
NOTE:
The Zero and Span adjustments on
the analyzer door are used only for
the calibration of the digital readout
for 0 to 100% oxygen.
The suppressed recorder ranges may
only be set up after the digital
readout has been calibrated. When
setting up a suppressed recorder
range, use only R41, R104 (setpoint)
and R88 (Span) for adjustments. DO
NOT RE-ADJUST THE ZERO AND
SPAN CONTROLS ON THE
ANALYZER DOOR.
c. Adjust ZERO Control so that
the reading on the digital
display or recorder is
appropriate to the downscale
standard gas. (The required
reading may be the actual
oxygen content of the
downscale standard gas or
may be an adjusted value,
depending on the relative
magnetic susceptibilities
involved. Refer to Section 3-
5c, page 3-10). If proper
reading is not obtained by an
adjustment of the ZERO
Control, refer to Section 6,
Service and Maintenance.
2. Set upscale calibration point as
follows:
a. Verify that front panel TEST
switch is set to NORM.
b. Pass upscale standard gas
through analyzer at same flow
rate as was used for downscale
standard gas. Allow gas to
purge analyzer for minimum of 3
minutes.
c. Adjust SPAN Control so that
reading on digital display or
recorder is appropriate to the
upscale standard gas. (The
required reading may be the
actual oxygen content of the
upscale standard gas or may be
an adjusted value, depending
on the relative magnetic
susceptibilities involved. Refer
to Section 3-5c, page 3-10). If
proper reading is unobtainable
by adjustment of the SPAN
control, refer to Section 6,
Service and Maintenance.
Repeat steps 1 and 2 to ensure no
interaction has occurred.
d. Calibration of Automatic Pressure
Compensation
Oxygen readout is automatically
corrected to within ±1% of fullscale for
barometric pressure variations within
±3% of the target value and is corrected
to within ±2% of fullscale for variations
within ±5% of the target value. The
target value 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 factory
setting is 0 psig (0 kPa). This setting is
suitable for applications where (a) the
analyzer exhaust port is vented directly
to the atmosphere, and (b) the
installation site is at or near sea level. If
conditions are otherwise, the pressure
compensation circuit must be re-
calibrated by the following procedure: