View source for Optical measurement of atmospheric carbon dioxide


==Team members==
Ta Na

Cao Yuan

Gao Yihan

Qi Kaiyi

Chen Yiming

==Idea==
Climate change has already become one of the most important challenges humanity faces. Carbon dioxide, the major greenhouse gas, is 'heating up' the Earth's atmosphere as they have an absorption peak in infrared wavelengths.

This project aims to build a portable and accurate carbon dioxide concentration measurement device.

===Possible measurement mechanisms===

#Spectroscopy. Carbon dioxide has absorption peaks at 15, '''4.3''', 2.7 and 2 &mu;m. With a laser/source of such wavelength and the correct filter, we could judge the concentration by absorption levels. See [https://www.vaisala.com/en/measurement/carbon-dioxide-co2-measurements?utm_medium=cpc&utm_source=google&utm_campaign=VIM-GLO-EN-MULTI-CO2-CO2_General_measurements&gad_source=1&gclid=Cj0KCQiAwtu9BhC8ARIsAI9JHam-XXVyI69He5NACVOxnr58TmdJ61t1D-_2SixL8PRPyUqYnOG6hdoaAsnOEALw_wcB viasala] for inspiration of a potential real-time reference design.
#Interferometry. Carbon dioxide has a slightly different refraction index for all wavelengths. By observing the change in interference patterns, we can tell if there is a change in carbon dioxide concentration due to a change in effective path length.
#

==Setup==
===Components===
*Source:
**A thermal/blackbody radiation/light source that can emit EM radiation at 4 micrometers. Can do it with a '''resistor''' or '''lamp'''.

*Sensor:
**Thermopile detectors: [[Media:Thermopile_G-TPCO-035 TS418-1N426.pdf|G-TPCO-035 / TS418-1N426]]: Thermopile detector with a built-in optical bandpass filter for light around 4&mu;m wavelength for CO<sub>2</sub> absorption
**low frequency chopper
**lock-in amplifier/oscilloscope

*Gas chamber (options):
**airtight acrylic box surrounding all optical components
**'''gas chamber with specific materials (Si/SiO2) transparent to 4 micrometer wavelength'''

*miscellaneous electronics
**breadboard, wires and soldering

*'''''to buy/acquire'''''
**halogen lamp
**1cm long gas chamber
**SiO2 microscope slips
**CO2 gas
**temperature sensor

*'''''to look up'''''
**extinction coefficient of CO2

==Measurements==
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