Eppendorf S Series 48S CO2 Incubator - Manual (Page 21)

21
New Brunswick Scientific User’s Guide
5. When the display instructs you to do so, close the door. An automatic 10-minute
countdown will start, to allow the chamber conditions to recover and the CO
2
sensor
signal to stabilize.
6. At the end of the countdown, the sensor signal will automatically be re-referenced.
The incubator will reopen the CO
2
valve to allow the CO
2
level to recover to the
setpoint value.
NOTE:
Pressing any key, or opening the door during the AutoZero will
automatically terminate the process and control of CO
2
will restart.
The incubator is now ready for use.
3.6 CO
2
Recovery
After a door opening, it should be possible for the actual CO
2
level to recover to around
4.8% in 2 to 2.5 minutes. The displayed CO
2
level takes 30 to 45 seconds more to catch
up with the actual level. This is because it takes approximately 45 seconds from the
time the gas enters the chamber to fully mix and become uniform inside the sensor.
The graph below (Figure 6) shows typical results for door openings between 10 and 45
seconds. The control system does this is by speeding the sensor reaction time when the
door is opened and then slowing it down to produce a more accurate reading after the
setpoint level is achieved.
Figure 6: Actual vs. Displayed CO
2
Levels