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CIRAS-DC Differential CO2/H2O IRGA, for PC operation

Part Number: CRS048Product Details

For over 25 years, PP Systems has been manufacturing high quality CO2 & H2O infrared gas analysers for researchers and customers from a wide variety of disciplines throughout the world. We are considered a leader in CO2 and H2O infrared gas analysis measurement instrumentation and our analysers are in use in over 100 countries worldwide. Our innovative Auto-Zero Measurement Principle ensures the greatest accuracy, reliability and long term stability that many of our customers have come to expect throughout the years.

Our CIRAS-2 SC and CIRAS-2 DC laboratory gas analysers feature a high technical specification and quality workmanship ensuring accuracy, precision and reliability. They are both designed to be operated through a standard PC for stand-alone operation. Having said that, an optional 12V lead acid battery can be supplied for both instruments for portable applications if required.

The CIRAS-2 DC is a dual channel infrared gas analyser for accurate, differential measurement of CO2 and H2O in µmol mol-1 from 2 gas streams (reference and analysis).

The CIRAS-2 DC is a dual channel, true differential infrared gas analyser featuring 4 independent gas analysers (2 for CO2 and 2 for H2O). The CIRAS-2 DC is capable of accurate, absolute measurement of CO2 and H2O in µmol mol-1 of two gas streams and displays the results as the absolute concentration of one gas stream (the reference) and the difference between the two gas streams. The analysers (reference and analysis) include an infrared source, gold plated and highly polished sample cells and detectors. The analysers act as absorptiometers measuring only in the 4.26µm (CO2) and 2.60µm (H2O) wavebands ensuring accurate, rapid and stable results. As such it is capable of resolving small differences between two gas streams in real time. The analysers are thermostatted and completely insulated to ensure accurate measurements under changing ambient temperatures. This eliminates problems associated with software corrections.

Our history and expertise in CO2 & H2O infrared gas analysis design speaks for itself. The design of the CIRAS ensures an inherent calibration stability. This has been confirmed by over 25 years experience of the technology. The CIRAS system does not require calibration. To ensure proper operation and calibration of the analysers, we do recommend periodic checks to confirm system integrity.

This type of instrument (true differential analyser) is the preferred option for plant photosynthesis and respiration measurements where differential concentrations need to be resolved to a high degree of accuracy and precision.

Measurement Ranges
  • CO2: 0-2000 µmol mol-1 (optimal); 0-10000 µmol mol-1 (maximum)
  • H2O: 0-Dewpoint
For measurements at elevated CO2 concentrations, the CIRAS-2 DC is factory calibrated up to 10000 µmol mol-1 as standard.

  • High precision, non-dispersive, differential infrared gas analysers for CO2 and H2O
  • CO2 Range: 0-2000 ppm (up to 10000 ppm)
  • Fast response
  • Analog & digital (RS232) linear output
  • Excellent stability achieved by built-in Auto-Zero facility
  • Fully compensated for changes in temperature, pressure and gas interactions
  • Built-in sampling pump with mass flow controllers
  • Insensitive to vibration, no moving parts ensuring high reliability
  • Photosynthesis and respiration
  • Plant/Crop physiology
  • Atmosphere & pollution CO2 monitoring
  • CO2 enrichment studies
  • Animal/insect physiology
  • Industrial process control
CIRAS-2 DC Differential CO2/H2O Infrared Gas Analyser product brochure


Part Number: CRS048
Air Sampling 100cm³/min using an integral DC pump. Both analysis and reference pumps fitted with mass flow controllers. The analyser may be used in open and closed systems.
Analog Output (CO2/H2O) 8 bit D/A converter giving 0.5% resolution. Output voltage 0-5V. Both minimum and maximum voltage are defined by user.
Analyser Control All analyser functions/controls are controlled by the PC (software supplied)
Analysis Method Non-dispersive infrared, configured as an absolute absorptiometer with microprocessor control of linearisation. The analysers simultaneously measure absolute CO2 and humidity of the reference and analysis gas streams. The CIRAS-2 DC has 4 independent analysers for true differential measurement.
Data Storage Internal battery backed RAM, stores up to 820 records. Memory is maintained during battery change.
Dimensions (H × W × D) 29cm × 10.5cm × 20.5cm
Environmental Sensor Inputs 3 input channels are available. There is integral conditioning of PP Systems' environmental sensors (%RH, Temperature, PAR, etc)
Housing Rugged, aluminum enclosure
Instrument Status Detection Indication of instrument malfunction, including low battery voltage (< 10.5V) through the RS232 output. Auto restart if momentary failure.
Linearity Better than 1.0% throughout the range, with calibration at 2000 ppm CO2 or 40 mb
Measurement Range CO2: 0-2000 µmol mol-1 (optimal range), 0-9999 µmol mol-1 (maximum range); H2O: 0-75 mb. Corrections are made for temperature, pressure and foreign gas broadening.
Operating Environment 0°C to 45°C, non-condensing. In dirty environments, external air filtration is required.
Power Consumption 12.0W (initial warm-up); 5.0W (normal operation)
Power Supply External 12V DC power supply with small ripple. Input voltage must not exceed 15V. An optional internal 12V battery can be supplied giving up to 2 hours continuous use.
Precision (Absolute) CO2: 0.2 µmol mol-¹ at 300 ppm, 0.5 µmol mol-¹ at 1750 ppm, 3.0 µmol mol-¹ at 9999 ppm; H2O: 0.015 mb at 0 mb, 0.020 mb at 10 mb, 0.030 mb at 50 mb
Real Time Clock Accuracy: Better than 1 min/month at 25°C; Operating Temperature: 0°C to 70°C
Recording Options By PC or by the instrument. Automatic logging at user selectable intervals between 10 seconds and 1 hour, controlled by internal real-time clock.
Response Time Electrical: 0.5 seconds; Display/Analog Output: 1.6 seconds; Pneumatic: < 5 seconds
RS232 Output Stored/current data output in standard ASCII format at 1200 baud
Stability (CO2 Analysis) Automatic Zero at regular intervals, corrects for sample cell contamination, source and detector ageing and pre-amplifier gain changes
Weight 2.7kg (optional, internal battery adds 0.6kg to the weight if used)

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