In this research, a new electro-optical-thermal modeling is proposed and built by simulation program with integrated circuit emphasis (SPICE). In particular, it is constructed for use in the non-dispersive infrared (NDIR) sensing technique of gas concentration. This model, based on the theory of circuitry and the Beer-Lambert law, includes various equivalent elements for the optics, sensor, and circuits. To build and investigate the validity of the proposed model, an NDIR for measurement of CO2 is built with the hybrid combination of a thermopile sensor with a specific wavelength filter, an infrared micro electro mechanical systems (MEMS) heater, an optical tube, amplification circuits with a chopper amplifier, advanced RISC machine (ARM)-based micro processing unit and discrete electronic devices. The thermal properties of the light source with periodic modulation have been studied from the output signal of a thermopile within the limit of modulation frequency. Based on the thorough measurements of output signals and transient responses, the thermal and optical parameters of the sensor and optical components for this model are extracted. The comparison of the simulation and experimental data of the NDIR measurement for different CO2 concentrations shows a great agreement with a maximum error of 0.27% at 3500 ppm. This approach allows for the development of a high-level sensor and circuit integrated simulation based on the most fundamental principles and multiple variables.

Articles you may be interested inSquare-shaped metal screens in the infrared to terahertz spectral region: Resonance frequency, band gap, and bandpass filter characteristics J. Appl. Phys.A photonic band-gap resonator to facilitate GHz-frequency conductivity experiments in pulsed magnetic fields Rev. Sci. Instrum. 77, 084702 (2006); 10.1063/1.2336761 Studies of surface two-dimensional photonic band-gap structuresMicrowave photonic band-gap ͑PBG͒ structures are well known for their superior ability to generate a band stop effect at a certain frequency range. Together with the microstrip transmission line structure, PBG can be utilized as a filter exceptionally well since the periodic perforation patterns can be implemented easily in the ground plane. In this research work, square perforations of different dimensions are constructed in the ground plane of a microstrip transmission line to achieve a double band stop PBG structure. Thus, the transmission ability of the microstrip line is being blocked at different frequency ranges to create a bandpass filter. It is found that the bandpass frequency is strongly dependent on the dimension to period distance ratio. It is demonstrated in both simulation and measurement that the bandpass region can be created at high frequency above 10 GHz.