Michael David

Incident Angle Approach to Sensitivity Enhancement for Ozone Sensor

The design and mathematical model of a reflective type optical gas sensor is presented. Light source is radiated at an incident angle for 10 cm gas cell with an internal diameter of 0.4 cm. At an incident angle of 1o, optical path length obtained is 342.7886 cm, at 27o incident angle, optical path length is 10.4926 cm and at an incident angle of 28o, optical path length is 9.9631 cm. The model is most efficient at lower incident angles, precisely between (1o and 27o). Effects of variation in diameter and length of gas cell are also demonstrated.

Pressure Dependence of Ozone Absorption Cross Section

Accurate value of absorption cross section is required for correct measurement of ozone concentration. Measurement of ozone has been done at different altitude and pressure. However, previous work has failed to establish significant relation between pressure and ozone absorption cross section. Therefore, this work aims to establish relation between pressure and maximum ozone absorption cross section via spectralcalc.com gas cell simulator. Simulation results show maximum absorption cross section 1.148×10-21 m2 molecule-1 and maximum absorption wavelength 255.442 nm are independent of pressure changes from 0.1 atm to 3.0 atm. Thus, measurement of ozone concentration at maximum absorption wavelength is strongly recommended due to negligible pressure dependence.

Sensitivity and response time of an ozone sensor

The use of optical retro-reflectors in improving the sensitivity and response time of an optical sensor based on optical absorption spectroscopy for the measurement of ozone gas is presented. Two optical retro-reflectors are employed in the design of a 30cm and 20 cm absorption gas cells. Our analysis shows that, in the 30cm gas cell, a sensitivity of 0.0451ppm and 0.0901ppm is achievable while in the 20cm gas cell we can achieve a sensitivity value of 0.0681ppm. However these sensitivity values are dependent on the optical density of the sensor. In general gas cell with wider diameters has potentials for a faster response time.

Optical path length, temperature, and wavelength effects simulation on ozone gas absorption cross sections towards green communications

Ozone is a green house gas. Ozone absorption cross sections have been reported with discrepancies and inconsiste ncies. In this paper, simultaneous effects of the optical path length and temperature variations on ozone gas absorption cross sections are investigated at different wavelengths. HITRAN 2012, the latest available line list on spectralcalc.com simulator, is used in this study to simulate ozone gas absorption cross sections in relation to the simultaneous effects of the optical path length and temperature at the wavelengths of 603 nm and 575 nm. Results obtained for gas cells with the optical path length from 10 cm to 120 cm show that the decrease in temperatures from 313 K to 103 K results in the increase in ozone gas absorption cross sections. At wavelengths of 603 nm and 575 nm, the percentage increase of ozone gas absorption cross sections is 1.22% and 0.71%, respectively. Results obtained in this study show that in the visible spectrum, at co nstant pressure, ozone gas absorption cross sections are dependent on the temperature and wavelength but do not depend on the optical path length. Analysis in this work addresses discrepancies in ozone gas absorption cross sections in relation to the temperature in the visible spectrum; thus, the results can be applied to get optimal configuration of high accuracy ozone gas sensors.

Investigation of the effect of inlet radius on the response time of a transmission type ozone sensor

The effect of inlet radius of a transmission type optical gas cell on its response time is reported. Six gas cells of varying lengths, and internal radius of 0.32cm were considered at first and then other internal diameters were also investigated afterwards. The effect of inlet radius is easily discernible at all velocities considered; however it is more pronounced at lower flow rates. At a velocity of 16.79cm/s of ozone gas, and for a target sensing time of ≤ 0.5 seconds; we observed that the inlet radius requirements for gas cells of varying lengths and varying internal diameters is not the same for a specific target sensing speed. The length and the internal radius of a gas cell are proportional to its inlet radius.