The CAI 602 Dual CO2 analyzer is designed specifically for dilution systems in which CO2 needs to be measured in low ppm levels. The analyzer uses a technique based on the infrared absorption characteristics of gases to measure concentration. A single beam of infrared energy is modulated and passed through a sample cell containing the gas to be measured. The beam emerges attenuated by the amount of energy absorbed by the gas in the sample. Changes in the concentration of the gas results in changes in the intensity of the beam. The remaining energy in the beam is passed serially through two cavities of an infrared detector containing the gas of interest and a mass flow sensor. Changes in the intensity of the beam change the pressure differential between the cavities and consequently the balance of the electrical bridge in the detector circuit. Electronic processing of the imbalance of the signal is used to generate an electrical output signal proportional to the concentration of gas measured.
The CAI Model 600 MHFID Analyzer is designed to continuously measure the total concentration of hydrocarbons or methane within a gaseous sample. The analyzers exhibit superior sensitivity and response time. The gaseous sample can be exhaust gases from an internal combustion engine, a combustion process or VOC abatement systems. This instrument can measure THC or CH4 in the ppm or percent levels. All internal components are maintained at the oven set temperature preventing condensation. Options for Internal Heated Sample Pump and Internal Zero/Span Solenoid Values are available.
This analyzer can be manually operated from the keypad or remotely via TCP/IP, RS-232C communications and discrete inputs. The analyzer display includes screen presentation of all analyzer alarms. Four levels of password protection are provided. For precision measurements, the analyzer's accuracy is increased by entering calibration curve fit polynomials. Automatic calibrations may be activated locally or remotely or at preset times. The analyzer may also display NO, NOX, NO2, and O2 via selectable time and hold commands
METHOD OF OPERATION
The approach utilizes CAI's standard 600 series analyzer with dual NDIR detectors. One detector is calibrated with methane and has a proprietary optical filter inserted into its light path which isolates a narrow portion of a methane IR spectrum peak which is away from absorption peaks of all other non-methane hydrocarbons. This provides a true methane only measurement. The other detector is also calibrated with methane to read total hydrocarbons (THC). Propane is measured on the THC channel and a C3H8 response factor is determined. As sample is introduced, it is split and methane and THC results are measured. Externally, methane is subtracted from the THC results and then multiplied by the propane response factor to determine the non-methane hydrocarbons relative to propane per Part 60, Method 25B.