Choosing a gas cell for an IRGAS gas analyzer system starts with the gases being measured, expected concentration range, required response time, sample temperature and pressure, and the chemical compatibility of the wetted materials. These factors help determine the required pathlength, internal volume, construction material, seals, optical windows, temperature control, pressure rating, and coupling method.
Start With the Gas Species and Measurement Range
The target gas species and expected concentration range determine the extent of infrared absorption the system must measure. A longer optical path increases the interaction between the sample and the infrared beam, thereby enabling lower-level measurements. A short path is better suited to stronger absorption or higher concentrations, where excessive pathlength could reduce the usable signal.
This is why no single gas cell is right for every IRGAS configuration. CIC Photonics offers long-path cells such as the Ranger and 4Runner, as well as direct-path Scout, CRV, and Cherokee options. The correct choice depends on the measurement problem rather than the model name alone.
Balance Pathlength, Internal Volume, and Response Time
Pathlength affects sensitivity, but internal volume and gas exchange affect how quickly a new sample reaches a representative reading. A long-path cell may improve absorption for trace-level detection, while a lower-volume cell can respond more quickly when the gas composition changes.
CIC Photonics reports that its long-path cells reach 90 percent gas exchange after two volume changes through a laminar-flow plenum design. The Ranger has a standard 9.6-meter pathlength and a 1.6-liter internal volume. The 4Runner has a standard 6-meter pathlength and a 0.6-liter internal volume, with a 0.34-liter option. Scout cells offer 2-, 5-, 10-, 15-, and 20-centimeter pathlengths with 2.8 milliliters of volume per centimeter. These differences help an engineer balance lower detection needs against response time and sample availability.
Match the Cell to Temperature and Pressure
The sampling conditions must remain within the selected cell’s operating limits. CIC Photonics lists continuous operating temperatures up to 315°C with certain seals and offers 120V and 240V heating packages controlled through a PID loop. The appropriate temperature, seal, and heating configuration must be selected according to the sample chemistry and operating conditions.
Pressure requirements can also narrow the selection. CIC Photonics long-path and direct-path cells can be pressurized to 300 psig (20 bar), depending on the optical windows. CRV pressure-rating options extend up to 135 bar (2,000 psi), and an embedded cryogenic cooling coil is available for operation down to -40°C.
Check Chemical Compatibility and Optical Windows
The sample must be compatible with the cell body, wetted surfaces, seals, and optical windows. CIC Photonics manufactures cells from 316L stainless steel, with nickel coating or electropolishing options. Cells can also be constructed from Hastelloy C22 or C276 for more demanding sample chemistries, including corrosive, high-pressure, and high-temperature applications.
- Gas composition and possible reaction products
- Required cell body material or surface treatment
- Seal compatibility at the intended temperature
- Window material across the required infrared range
- Leak-rate and containment requirements
Available window materials include sapphire, AgCl, BaF2, CaF2, germanium, KBr, ZnSe, and ZnS. Selection should be based on the spectral range and sample chemistry, not only on general durability.
Confirm How the Cell Will Connect to the System
Mechanical and optical fit are part of gas cell selection. Scout and CRV cells have adjustable-height options for different spectrometer sample compartments or table mounting. Scout and Cherokee cells can also support fiber-optic coupling when the measurement point needs to be separated from the spectrometer. Sampling ports, purge arrangements, sensors, and mounting space should be confirmed before the configuration is finalized.
Build the IRGAS Configuration Around the Sample
A reliable IRGAS gas analyzer system is configured around the sample and measurement objective. Review the target species, concentration range, response requirement, temperature, pressure, materials, windows, and integration details with CIC Photonics before choosing a gas cell. Contact the team at request@cicp.com or (505) 343-9500 to discuss the correct configuration.