Non-Dispersive Infrared Gas Measurement
Title: Non-Dispersive Infrared Gas Measurement
Authors: Jacob Y. Wong and Roy L. Anderson
Publisher: International Frequency Sensor Association (IFSA) Publishing
Formats: printable pdf (Acrobat) and print (hardcover),120 pages
Pubdate: 19 June 2012
Price: 79.95 EUR (e-book in pdf format) and 89.95 EUR (print hardcover book). Taxes and shipping costs are included.
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Written by experts in the field, the Non-Dispersive Infrared Gas Measurement begins with a brief survey of various gas measurement techniques and continues with fundamental aspects and cutting-edge progress in NDIR gas sensors in their historical development. It addresses various fields, including:
Providing sufficient background information and details, the book Non-Dispersive Infrared Gas Measurement is an excellent resource for advanced level undergraduate and graduate students as well as researchers, instrumentation engineers, applied physicists, chemists, material scientists in gas, chemical, biological, and medical sensors to have a comprehensive understanding of the development of non-dispersive infrared gas sensors and the trends for the future investigation.
Infrared spectroscopy provides the analytical laboratory with essential capabilities to identify and to quantify components of gas mixtures in a relatively straightforward manner. Except for symmetric diatomic species, most molecules are “IR active” that is, they absorb IR light at specific energies associated with that molecule’s vibrational and rotation modes. Simple molecules have a few predominant absorption energies and are easy to identify, while more complicated molecules with many bonds have many absorption peaks. To cover the full range of possible absorption energies, laboratory instruments initially employed dispersive elements, typically gratings, to scan over the wavelengths of interest. Today, Fourier-transform infrared (FTIR) spectroscopy has replaced most dispersive IR spectrometry due to improvements in speed and the signal-to-noise ratio but at the expense of instrumental complexity.
The impressive analytical power of IR spectroscopy can be distilled into a tiny sensor for a restricted, but nevertheless very useful, set of chemical vapors. Non-dispersive infrared (NDIR) sensors use bandpass filters to select one, or at most a few, energy bands corresponding absorption by carbon dioxide, water, hydrocarbons, etc. Although the concept is simple, the task has proved to be elusive for constructing an NDIR sensor that maintains its calibration in spite of aging and environmental factors. Over the past four decades, Dr. Wong has been on the quest to perfect NDIR sensing, yet in very practical designs. This book reflects his journey, and more recently that of his coauthor, to do just that.
Non-Dispersive Infrared (NDIR) - Gas Measurement begins with a brief survey of various gas measurement techniques. Sensor discovery and development continue to be the subject of numerous professional journals and meetings. The need for improved sensor technology in residential, commercial, automotive, military and industrial sectors has driven this interest. The majority of published papers report the observation of sensing based upon a property change of some material when it interacts with a gas (termed “Interactive” in this book). The reproducibility of such a sensor depends upon the stability of the material, which is nearly always subject to degradation over time. Physical-based sensors, on the other hand, rely upon detecting a measurable change of some physical interaction of the gas with the sensor (termed “Non-Interactive” in this book). Most high-quality analytical instruments depend upon physical interactions. NDIR sensors fall into the category of physical based sensors, which are usually the most reliable over time, if properly engineered.
Chapter 2 gives an interesting history of infrared gas sensing and includes some well-known pioneers of spectroscopy such as Sir William Herschel and John Tyndall, but also includes the eminent Alexander Graham Bell just a few years after his invention of the telephone. One of the first practical applications of infrared gas sensing was Tyndall’s quantitative measurement of carbon dioxide in the human breath (1864). Curiously a hundred years later, Dr. Wong led a team at Hewlett Packard that finally solved the issues of medical CO2 measurement to create a practical breath monitor that served the medical community for almost two decades (Chapter 3). The development and naming of the Capnometer show how good business opportunities arise from clever science, even when initial goals are thwarted.
Dr. Wong is no stranger at the U.S. Patent Office and holds more than one hundred patents. Chapter 4 enumerates a series of NDIR patents, dominated by Wong that heralded the birth of practical CO2 sensors and enabled Demand Control Ventilation (DCV). Because methods used in the medical Capnometer could not be afforded by DCV installations, these simpler sensors suffered calibration drift. Without Dr. Wong’s scheme of Automatic Background Correction (ABC), the expense of frequent recalibration by field technicians would have sorely limited DCV applications.
Very recent design innovations promise to usher a proliferation of NDIR sensors for DCV, humidity control and safety purposes. Chapter 5 shows that issues involving the inevitable degradation and drift of components can be compensated. Thus, the intervals between calibrations could be greatly extended or even eliminated for many applications. Until now, the widespread implementation of DCV has been hindered by maintenance costs. If calibration is desired, Dr. Wong has invented a means to accomplish this using only ambient environmental air rather than bottles of calibration gas. Moreover, absolute humidity measurement has been elusive due to the difficulty in maintaining calibration. The improvements discussed in this chapter have the potential to transform the HVAC industry. Large-volume manufacture should drop costs and encourage even more widespread deployment. Very high volumes will allow microfabricated emitters and detectors to replace their less efficient predecessors. It is possible to conceive of inexpensive self-checking safety sensors for fire, methane, carbon monoxide, pollutants and toxic gases.
The reader interested in gas sensors will benefit from the following material. Much of what is known about NDIR sensing has been kept proprietary and very little has been written about its development. The authors’ homey and wandering account of their developments and exploits may be amusing at times, but attest to the perseverance and good fortune required for success.
R. J. Bruce Warmack,
Senior Research Scientist, Oak Ridge National Laboratory
Oak Ridge, Tennessee, USA
Dr. Wong did his undergraduate work at Princeton University (AB ’63) and his graduate work in infrared lasers research at Stanford University (Ph.D. ’67). He joined Hewlett-Packard Company in 1967 and stayed there until 1978. After a short stay in the aerospace industry, he started a total of three companies all specializing in the R&D of advanced NDIR gas sensors. The third and latest company he started in 2003 was Airware Inc. which is still in business today. Over the years Dr. Wong has published over 40 research papers in major scientific journals and authored over 100 US and International patents worldwide.
Mr. Anderson has an undergraduate degree in chemistry from Illinois Wesleyan University (BA ’79) and a Juris Doctor degree from The George Washington University (JD ’82). He began with, and became a partner in, Lyon & Lyon, where he practiced patent law litigation and prosecution until 2000, when he left to practice on his own. He began working with Dr. Wong in the mid 1980’s. Today he is a partner with Wagner, Anderson & Bright, P.C., he has worked on and filed dozens of patents issued to Dr. Wong relating to advanced NDIR gas sensors.
Chapter 1. NDIR Gas Measurement in a Nutshell
Chapter 2. A Historical Perspective
Chapter 3. The First 25 Years of Development after Dawn
Chapter 4. The Next 30 Years of Development
Chapter 5. NDIR Gas Measurement Today
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