CIRAS-3 Operation Manual V. 1.09
69
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.
