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9.4 CO
2
Calibration
The DH Autoflow infrared CO
2
sensor may be calibrated using one of three techniques: CO
2
control, CO
2
sensor and CO
2
injection calibration. The CO
2
control and CO
2
injection calibration procedure are easily
performed on the front panel similar to the temperature offset requiring no tools. The CO
2
sensor internal
procedure is more in depth requiring approximately 15 minutes to perform.
9.4.1 CO
2
Control Calibration
CO
2
Control Calibration can be performed anytime the CO
2
fyrite measurement doesn't correlate to the
front panel display. However, this calibration SHOULD NOT BE PERFORMED MORE THAN
ONCE PER WEEK. Sensor calibration should be performed if the CO
2
fyrite measurement doesn't
match the display 0.3 percent after one week. Before doing the following calibration, check
and change, if necessary, the incubator in-line filter found within the control center.
When unit has stabilized at the operational temperature and CO
2
percentage, take a CO
2
fyrite
measurement and, if necessary, perform the following:
In run mode - green LED above mode key is on & not blinking.
Press "SEL" to indicate LED next to CO
2
percent display.
Press and hold UP key, CO
2
display alternates between “ADJ” and the CO
2
percentage.
Press both UP and DOWN keys simultaneously, (clears all previous offsets).
Fyrite the incubator to determine actual CO
2
percentage (compare the display CO
2
to the CO
2
Fyrite
measurement. If these two readings have a difference of less than 1.0 percent, proceed to enter the
CO
2
Fyrite value. If the difference is greater than 1.0 percent, proceed to CO
2
sensor calibration.
Press UP or DOWN key to indicate same CO
2
percentage as the Fyrite measurement.
Press "SEL" to set current value and exit calibration.
NOTE: When the independent measurement is more than 0.3% different from the display, only offset one half
the measured difference. For example, the display shows 5.0% and you measure 5.4%, offset the display 0.2%,
(1/2 of 0.4), then allow the chamber to stabilize. Recheck and adjust the display if needed.
9.4.2 CO
2
Sensor Calibration (Zero/Span/CAL. INJ.)
There are 2 sensor (zero/span) calibration routines available to the lab professional. An “open door” routine
involving opening the outer and inner door to zero the sensor. This routine also automatically calibrates to the
CO
2
injection rate during the injection for the span portion of the sensor calibration. It is recommended that this
routine be used during the initial setup of the incubator, if the set-point of the system is changed or if other
changes are made on the incubator affecting the CO
2
sensor. The second option is a “closed door” routine.
This routine allows calibration of the sensor with out opening the door avoiding undue exposure to the cultures
that may be in process. This routine injects “fresh air” into the detector head of the sensor to calibrate zero.
The chamber air is then allowed back into the detector head to calibrate the gas span that is detected. The CO
2
injection calibration must re-run after the closed door calibration to optimize CO
2
recovery. The closed-door
routine option is activated through the Options menu and must be turned off to use the open door routine.
OPEN DOOR CO
2
SENSOR CALIBRATION ROUTINE (Default CO
2
calibration routine):
Zero
calibration
Make sure unit is in Run mode, the green LED above the mode key should be on and not blinking.
Press the "SEL" key to indicate the LED next to the CO
2
display.
Press the
▼
until "dor" flashes in the temperature
display. Open the outer and inner doors to release the
CO
2
from the chamber. When "dor" starts flashing after 90 seconds close the doors. Display shows old
value if other than zero then zeros out.
This automatically starts the span calibration. The CO
2
display will show the following in order:
NOTE: If the value in the display is greater than 0.2 prior to the display zeroing, the zeroing portion of
the routine should be run again. The current routine can be completed. Then run the sensor calibration
again to ensure a proper zero. If value was 0.2% or less, go on to the SPAN portion of the calibration.
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