NuAire NU-5800, Operation And Maintenance Manual

Page: 35 / 48

OM0211 Page 35 of 48
Rev 3 March 2013
9.3 Setting Air Injections
If there is still some undesired condensation in the chamber when the door and perimeter heaters are set for the desired
result, the air injections can be adjusted. There is a control for length of the air injection labeled, Air Inject Time, and the
frequency that air is injected called, Air Inject Cycle. These controls are described in more detail in the "General Options"
section of the Service Settings menu. The default is 5-second injections every 1 minute. Start by increasing the length of
the injection by a few seconds at a time then increase the frequency if needed. If the humidity in the chamber is less than
desired, reduce the Air Inject Time.
9.4 CO
2
Calibration
The DH infrared CO
2
sensor may be calibrated using one of four techniques: Open Door CO
2
, Closed Door CO2, Off-Set, and
CO2 injection calibrations. CO2 calibrations can be performed in approximately ten minutes, by accessing the CO2
calibrations menu in “Service Settings” and following the on screen instructions. To perform Off-Set, Open Door, and Closed
Door calibrations attach an independent CO2 measurement device to the Sample Port in the front of the unit before the
calibration begins.
9.4.1 CO
2
Off Set Calibration
CO
2
Off Set Calibration can be performed anytime an independent 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 an independent measurement, if it doesn't match the display 0.3 percent within one
week after a sensor calibration. Before doing the following calibration, check and change, if necessary, the Incubator
in-line filter found within the Sensor bay.
When unit has stabilized at the operational temperature and CO
2
percentage, take an independent measurement
and, if necessary, perform the following:
•
In “Service Settings” enter the CO2 Calibrations menu.
• Press the “CO2 Offset Calibration” text button
• Use an independent instrument to determine actual CO
2
percentage (compare the display CO
2
to the
independent measurement).
If these two readings have a difference of less than 1.0 percent, proceed to enter the CO
2
Fyrite value.
(See * Note below)
If the difference is greater than 1.0 percent, it is recommended to perform a CO2 Open Door Calibration.
•
Enter the value measured by the independent device
•
Exit and Save to retain this value.
*Note: When the display value is more that 0.3% different from the measured value, offset display
1/2 the difference measured.
Allow the Incubator to stabilize back to set point, then measure the CO
2
in the chamber again.
Offset the display again if necessary.
9.4.2 CO
2
Sensor Calibration (Zero/Span/CAL. INJ.)
There are 2 sensor (zero/span) calibration routines available to the lab professional. The first option is the “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
system.
The second option is a “closed door” routine. This routine allows calibration of the sensor without 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.
9.4.3 Open Door CO
2
Sensor Calibration Routine
The CO2 inject rate is automatically calculated from the CO
2
injection made during the span calibration making it
unnecessary to run the separate “Injection Calibration”. The injection is dependent on the proper gas pressure and
factory set flow rate. Any changes in either will result in a change to the value reached during this injection.