Partial Pressure of CO2

Model AS-P3

The Apollo SciTech® 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), a laser-based CO2 analyzer (LI-COR LI-7815), or an infrared CO2 analyzer (LI-850 or 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-7815 detector in model AS-P3 can be replaced with a LI-850 or LI-7000 analyzer (pCO2 ranges 0 – 20,000 µatm).


  • Power Supply: 110 or 220 VAC depending on country of destination
  • Repeatability: better than 1 ppm
  • Communication: USB port
  • Environment Required: Indoor, outdoor, or shipboard

Optional Sensors

  • Garmin GPS 19x HVS
  • Airmar Weather Station 200WX
  • Honeywell Durafet III pH Probe
  • Aanderaa Oxygen Optode 4835
  • Turner Designs Cyclops-7F Chlorophyll Probe