Reliable gas detection is essential for industrial control, health, and environmental protection. Gas detection based on the infrared absorption principle offers high selectivity but faces challenges in precision and stability. Non-dispersive infrared (NDIR) and gas filter correlation (GFC) analyzer are pivotal for precise gas detection among various measurement devices. In recent years, infrared technology has rapidly advanced due to efforts from major research institutions, companies, and universities. This study establishes a model to describe the relationship between the infrared light source, wavelength, GFC wheel, center wavelength, filter bandwidth, the optical path length of the air chamber, gas volume fraction, and the measurement/reference signals. This model provides insights for amplifier circuit design. We analyze the measurement accuracy and the influence of temperature variations on the system using the response function of the analyzer. Our design proposal enhances primary design stages, guiding the development of NDIR and GFC analyzer and demonstrating the practical application of our approach.

The NDIR and GFC analyzer comprises six main components: infrared light source, GFC wheel, filter, air chamber, detector, and main circuit system (Fig. 1). To optimize and evaluate our design proposal, we develop a model to describe their relationships with measurement and reference signals. Firstly, we model the infrared light source, GFC wheel, center wavelength, filter bandwidth, the optical path length of the air chamber, and gas volume fraction, deriving expressions for measurement and reference signals. MATLAB simulations based on the HITRAN spectra database are employed to simulate NDIR absorption under varying gas volume fraction, temperature, pressure, and other conditions (Fig. 3), providing insights for amplifier circuit design. We further optimize our design proposal by analyzing the system’s measurement accuracy through the response function (Fig. 4). Simulations also assess gas absorption under different temperatures, quantifying errors in CO₂ volume fraction retrieval due to system temperature variations (Fig. 6 and Table 1). This underscores the necessity of ±0.1 ℃ air chamber temperature control to ensure analyzer performance. Practical experiments confirm the effectiveness of our method in guiding the practical design of NDIR and GFC analyzers.

The response function, representing the ratio of measurement and reference signals, is calculated for varied gas volume fraction under specific conditions (Fig. 3), affirming the suitability of selected parameters for circuit system design. System measurement accuracy is confirmed to be within 1×10^-6 through analysis of the response function (Fig. 4). Temperature variations of 10 ℃ result in up to 9×10^-6 error in retrieved CO₂ volume fraction (Table 1), underscoring the critical need for air chamber temperature control to maintain analyzer performance. Theoretical simulations demonstrate detection limits below 0.075×10^-6, indication errors of 0.19%, and precision of 0.11%, with zero and span drifts below 0.033% and 0.3% of the full scale, respectively (Table 2). Theoretical simulations demonstrate detection limits below 0.075×10^-6, indication errors of 0.19%, and precision of 0.11%, with zero and span drifts below 0.033% and 0.3% of the full scale, respectively (Table 2).

We build a model describing the relationship between optical components, wavelength, filter bandwidth, and gas volume fraction with measurement and reference signals, which is crucial for amplifier circuit design. The error in retrieved CO₂ volume fraction can reach up to 9×10^-6 due to an external temperature variation of 10 ℃ in the system. Therefore, a temperature control system for the air chamber is necessary to ensure the performance of the system.

With the help of theoretical simulation, detection limits, indication errors, and relative standard errors of the practically designed gas analyzer can be achieved better than 0.075×10^-6, 0.19%, and 0.11% can be realized, respectively. Zero and span drifts are no more than 0.033% and 0.3% of the full scale. The volume fraction of CO₂ is well correlated between NDIR with the laser measurement technology, with a correlation coefficient (R²) of 0.94. Using this simulation method, we guide the practical design of NDIR and GFC analyzer for CO₂ detection and prove the application value of the simulation method.