Partial Pressure of CO2

Model AS-P3

Apollo SciTech's Underway pCO2  system, model AS-P3, has been developed and tested for underway measurements (i.e., real-time while the vessel is sailing) of the partial pressure of CO2  (pCO2 ), pH, and dissolved oxygen (DO) in surface water, atmospheric CO2  as well as water salinity, temperature, and position. Water sample is forced into the equilibrator by a shipboard pump. Equilibrated air is drawn from the equilibrator and dried with an electronic cooling system and a Nafion dry tube. It is then quantified with a CRDS CO2  analyzer (Picarro G-2301) and/or an infrared CO2  analyzer (LI-7000) before returning to the equilibrator. The shower-head equilibrator is effective (response time 2 min). The equilibrator is completely sealed from the outside room air.

It has been tested in both high (up to 3000 µatm) and low (less than 100 µatm) pCO2  environments.

The LI-7000 detector in model AS-P3 can be replaced with a LI-850 analyzer (pCO2  ranges 0 – 20,000 µatm) or LI-7815.


  • Power Supply: VAC, automatic switch
  • Repeatability: better than 1 ppm
  • PC system: Windows XP or higher
  • Communication: USB port
  • Environment Required: Indoor, outdoor, or shipboard


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