Eppendorf Galaxy CO2 Sensor - Manual (Page 74)

Equipment options
Galaxy
® 170 R/170 S CO
2
Incubators
English (EN)
74
8. By controlling the Duty Cycle of the N
2
valve, Oxygen Control can be tailored to achieve programmed
Oxygen and Carbon Dioxide levels at approximately the same time.
12.4.3 Operating guidelines
We recommend that you repeat the OXYGEN SENSOR-REF TO ATMOSPHERE procedure (see Setting up
the N
2
tank on p. 72) Step 3, and further details (see Referencing to atmosphere on p. 74) once a month to
ensure that any long-term drift in sensor output will be corrected. Be sure to do it at the chamber operating
temperature.
When you are cleaning the chamber, be very careful not to wet the oxygen sensor or CO
2
sensor. Never use
solvents on the sensor membrane; rather, be sure to cap the hydrophobic filter before you clean. It is good
practice to replace the filter each time you clean the incubator chamber, to avoid the possibility of filter
contamination.
Under normal relative humidity conditions (95 - 99 %), the oxygen sensor’s performance should not be
affected. If, however, liquid condenses around the sensor, gas flow may become restricted, giving the
sensor a low signal. This may occur if there is a large liquid spill inside the chamber or if the incubator is
turned off while it is fully humidified. Should such condensation appear, normal operation can be restored
by:
• removing the humidity tray,
• drying the chamber completely,
• and then running the incubator at 37 °C for one hour.
This will dry out the sensor(s). The humidity tray can then be reinstalled and the incubator can be safely
re-humidified.
12.4.4 Referencing to atmosphere
The oxygen sensor is a self-powered electrochemical cell that has a finite life dependent on the ambient
oxygen level. A typical lifespan is 1 - 2 years at atmospheric levels. During the sensor’s lifespan, the signal
produced will slowly degrade until it is ultimately unusable. For this reason, we recommend that you
reference the sensor to atmospheric oxygen levels on a monthly basis.
The OXYGEN SENSOR-REF TO ATMOSPHERE procedure has three possible outcomes. The first is that
the procedure was completely successful, and no further action need be taken until the following month’s
test. The second and third outcomes are presented in detail in (see
Replace sensor soon on p. 75) and (see
Replace sensor now on p. 75).
For instructions on removing and replacing the sensor (see Removing and replacing O
2
sensor on p. 76).
At low oxygen levels, the CO
2
and O
2
levels may not have fully recovered within the Alarm
limits after the 15-minute “Delay in arming after door opening.” This time period can be
increased (in the ALARM screen) to suit individual circumstances.