CIRAS-3 Operation Manual V. 1.09 69 support@ppsystems.com
For instance, if the CIRAS-3 is operating for long periods throughout the day and at high CO
2
concentrations, we would expect that when you turn on the system the following day the CO
2
cartridge
will be low and it is safe to change out. If the CIRAS-3 is operating for just a short period of time
throughout the day (i.e. less than 4 hours in total) and at approximate ambient CO
2
concentration (i.e. 390
µmol mol
-1
), you will likely have enough CO
2
to get you several more hours of use the day after a CO
2
cartridge is installed.
If unsure of how much CO
2
is still available from the cartridge, we recommend the following simple test:
1. Power up the CIRAS-3 system as described above.
2. After warm up and with the numeric or graphical display on the console LCD, press Controls
(F3).
3. Set the “CO2 Reference” to 2000 and hit Accept (F2).
Monitor the CO2r (CO
2
Reference) value. After a minute or so, it should reach 2000. If the CO2r reaches
2000 you can proceed with measurements without having to change out the CO
2
cartridge. Note, keep
an eye on the CO2r during your measurements and if you observe the CO2r starting to drop slowly this is
a good indication that the cartridge is exhausting and we recommend changing it. If it does not reach
2000, this is a good indication that the CO
2
is low or starting to get low and it is safe to change out the
cartridge as the CO2r will likely become unstable within a short period of time.
Another quick and simple check to see if you
have a pressurized CO
2
cartridge is to remove
the entire CO
2
cartridge holder and regulator
assembly from the CIRAS-3 console. To do so,
turn the cartridge holder a quarter-turn counter-
clockwise and pull the entire assembly out from
the console. Next put a small piece of flexible
tubing on the end as shown here and place the
tip of the tubing in the water. If a CO
2
cartridge
is pressurized you should see a steady bubble at
approximately 1 second intervals. If the CO
2
cartridge is not pressurized you will not see any
bubbling indicating that it is safe to change out.
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