NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
Photoacoustic Spectrometer for Accurate, Continuous Measurements of Atmospheric Carbon Dioxide Concentration
Published
Author(s)
Joseph T. Hodges, Zachary D. Reed, Brent A. Sperling, Roger D. van Zee, James R. Whetstone, Keith A. Gillis
Abstract
We have developed a portable photoacoustic spectrometer that offers routine, precise and accurate measurements of atmospheric carbon dioxide mixing ratios. The spectrometer is temperature controlled, continuously samples and dries atmospheric air, and employs an intensity-modulated distributed feedback laser and fiber amplifier operating near 1.57 µm. For measurements of carbon dioxide mixing ratio in air, we demonstrate a measurement precision (60 s averaging time) of 0.15 µmol mol-1 and achieve a standard uncertainty of 0.8 mol mol-1 by calibrating the analyzer response in terms of certified gas mixtures. We also investigate how water vapor affects the photo-acoustic signal by promoting collisional relaxation of the carbon dioxide.
Hodges, J.
, Reed, Z.
, Sperling, B.
, van, R.
, Whetstone, J.
and Gillis, K.
(2014),
Photoacoustic Spectrometer for Accurate, Continuous Measurements of Atmospheric Carbon Dioxide Concentration, Applied Physics B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915516
(Accessed October 9, 2025)