Co2 Injection Calibration; System Auto Zero Calibration Function - NuAire NU-5510 Operation And Maintenance Manual

9.4.3 CO Injection Calibration
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The CO
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the gas injection time required to recover the CO
recovery time should be as minimal as possible with virtually no overshoot. Verify the CO
calibration prior to performing an injection calibration. The injection calibration is not required
after an "Open Door" sensor calibration since it is performed automatically during this routine.
The injection calibration should be performed after a "Closed Door" sensor calibration when
possible, if CO
disturbed.
The following steps should be taken for the CO

Press "SEL" to indicate LED next to CO

Press and hold ▲and ▼ keys simultaneously for three seconds. "CAL" and current indicated
CO % will blink.
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
Open door for at least 1 minute to evacuate the CO
display should be below 1% before closing the door to continue the routine

Press and hold ▲ and ▼ keys simultaneously again to start auto calibration procedure.

Observe display, which will indicate the following sequence:

Press "SEL" to set current value and exit calibration.

If necessary, open glass door to vent excess gas.
9.4.4 CO

System Auto Zero Calibration Function

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This Incubator is programmed to automatically check and adjust the zero calibration of the CO
sensor. HEPA filtered room air is pumped through the sensor detector cell for 2 minutes. The CO
reading is checked at this time. If it 0.5% or less different than the current zero the sensor will use
the new value as zero. When the value is greater than + 0.5%, the auto zero routine is aborted and
an ACF alarm is sounded. See Section 11.0 on Trouble Shooting for responses to this alarm.
The auto zero routine is scheduled to be initiated 12 hours after the Incubator is turned on
and then every 24 hours thereafter. This timing is structured to run the auto zero routine
daily at a time that would be considered "off hours". The timer for this routine can be reset
at any time by simply turning the Incubator off then back on. Power failures will reset the
timer.
This routine is essentially transparent to the operation of the Incubator and the factory supplied
options like the chart recorder or the printer outputs while it is running. After the routine is done
the CO level will be reduced by about 0.2% to 1.0% depending on the amount of air that has be
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injected to perform the routine. The routine can run as long as 7 minutes because it will try to
perform the zero function up to 5 times before declaring an "ACF" alarm. If any calibrations are
attempted during this routine "SLF" shows in the display and the calibration is inhibited until the
routine is complete. An independent monitoring system will record a minor shift in CO
temperature during the routine. This happens because the air injected into the sensor, during the
purge and while the sensor is performing the zero function, is passed into the chamber.
This routine compensates for minor shifts in zero due to electronic drift. Regularly
scheduled checks of the calibration by an independent instrument must still be performed.
9.5 To abort the Auto Zero routine open the inner glass door and close it again.
OM0135
injection calibration can be performed separately from zero/span calibration to optimize
supply pressure of the Incubator is changed, or is the CO
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a) dLY - Wait for door delay, prior inject delay, temp. in range.
b) INJ - Inject CO for fixed time period according to the set point
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c) dLY - Wait for post inject diffusion.
d) End - Done with Calibration
level to set point after a door opening. The
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injection calibration:
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percent display.
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from the chamber. The value on the
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sensor
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flow control valve is
2
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and
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