CO2 & H2O gas analysers

The heart and soul of any photosynthesis system is the analyser. Accurate, reliable and stable measurement and control of CO2 and H2O are critical for high-level research. The CIRAS-3 is a “true differential analyser” featuring 4 independent, non-dispersive gas analysers for accurate, simultaneous measurement and control of both CO2 and H2O. This is a significant advantage over “gas switching” systems and a major requirement for most researchers. For enhanced reliability, there are no moving parts such as chopper motors or filter wheels. The gas analysers include an infrared source, highly polished, gold plated sample cells and detectors that are optimised for CO2 (4.26 µm) and H2O (2.60 µm). The analysers act as absorptiometers measuring infrared absorption only. The optical bench is temperature controlled and pressure compensated ensuring the most accurate measurement of CO2 and H2O under changing ambient conditions.

Measurement ranges

  • CO2: 0
  • µmol mol-1 – 10,000 µmol mol-1
  • H2O: 0 – dewpoint


The design of the CIRAS-3 ensures an inherent calibration stability that has been confirmed by over 35 years of experience in gas analysis technology. The CIRAS-3 features an innovative Auto-Zero function that allows for fast warm-up, adaptation to changing ambient conditions and excellent stability. In short, expect accurate, reliable and stable calibration for many years without the need for time-consuming, expensive recalibration. The Auto-Zero function minimises effects on span (gas sensitivity) of sample, source aging, changes in detector sensitivity and changes in pre-amplifier gain. Periodic system checks are simple and recommended to confirm system integrity and calibration.