Fundamentals of Gas Sensors

John Blyler | Mar 15, 2021

Detecting the presence of harmful gases was a necessity for early miners as well as manufacturers and consumers at the start of the industrial revolution. One of the first gas detectors was a flame safety lamp (or Davy lamp) invented by English inventor Sir Humphry Davy in 1815. The Davy lamp was used to detect the presence of methane (firedamp) in underground coal mines.

Yesterday's gas sensing techniques can't hold a candle to today's methods. The consumer and industrial Internet-of-Things (IoT) era have enabled sensor-rich gas detecting tools to deal with a variety of harmful, radioactive, and explosive types of gases. The most common gas technologies include Molecular Property Spectrometer (MPS), Pellister (cat-bead), Nondispersive infrared (NDIR), Electrochemical (echem), and Photoionization Detector (PID).

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Each one of these is designed for a specific type of gas. For example, the MPS, Pellister, and NDIR are used to detect various hydrocarbons (flammable/combustible gases). Conversely, echem sensors and PID are better at detecting various toxic gases and volatile organic compounds (VOCs).

How should engineers approach the task of selecting and implementing gas sensor technologies into their IoT/IIoT designs? To answer these questions, Design News met with experts at NevadaNano. What follows is a portion of that discussion.

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Design News: How should designers and manufacturers go about selecting the right gas sensor?

NevadaNano: Selecting the right sensor all comes down to the type of gas you need to measure and the environment in which the sensor will operate. For gases such as carbon monoxide and hydrogen sulfide, it's best to use toxic gas electrochemical (or echem) technology sensor systems. PID technology is a good choice for those gases that cannot be detected by echem sensors, such as toxic Benzene gas. For the detection of hydrocarbon (combustible/flammable) gases, options would include MPS, NDIR, and Pellister technologies. Here a good set of design requirements with which to start:

1) What gas or gases are to be detected?

2) What is the needed range of detection?

3) What environmental conditions or constraints might affect the design?

Each of these previously mentioned gas sensing systems have their own advantages and disadvantages. It is important to understand these differences before selecting the technology to be used for a given application.

Design News: How are gas sensors used in industry?

NevadaNano: As you’d imagine, there are many variables – such as operational scenarios – to consider when selected the most appropriate gas detector technology. Many industrial gas detectors allow for either fixed or portable detection. Selecting the right industrial gas detector requires an understanding of the limitations and strengths of each sensor type.

Portable and handheld devices can be used for single gas or multi-gas sensing. The latter may incorporate multiple technologies into one device. These types of detectors are generally used for the protection of the person wearing the device.

Fixed detectors are normally single gas sensing devices that are often hard-wired for 24/7/365 monitoring in a vast range of industrial or commercial applications.

Design News: How do they fit into the IoT and IIOT platforms?

NevadaNano: Data has become a key tool for analytics across a wide range of applications. The greater the amount of analyzed and actionable data, the more likely it that users will be able to make informed decisions. Historically, gas sensors provided gas levels at a local level. The same was true with portable instruments, where only the immediate user would have access to the data. Finally, for fixed instruments, the gas levels would be isolated to the facility.

By incorporating sensors into IoT and IIOT platforms, gas-related data (e.g., the levels of harmful gases) can be transmitted across the globe providing real-time data for both portable and fixed style of monitors. For example, a simple Bluetooth-enabled gas detector and the corresponding app will supply the local user with updated readings that can then be automatically shared wirelessly with their supervisor located in another nearby or a great distance away.

Design News: What does the future hold for gas sensors?

NevadaNano: Decades-old sensing technology is still being used today and in the foreseeable future. However, sensor advancements are leading to new market technologies, such as the Molecular Property Spectrometer (MPS) flammable gas sensor.

Additional improvements are being made to reduce the frequency of calibrations. More data will be provided to include leak rates, duration of a gas leak, source of the gas leak, and much more. With semiconductor MEMS and nano-based improvements, the size and cost of sensors will continue to decrease. This reduction will enable the deployment of a greater number of sensors providing more and more data.

New applications are being created globally. The legislative focus to reduce global warming is a big driver. For example, there are now tighter restrictions against gas leaks on a seemingly endless length of natural gas pipelines around the world. Using sensors to pinpoint potential methane gas leaks from such pipes not only improves the impact on the environment but helps reduce product loss, thus improving profits to the industry.

The reduction in sensor cost, improvements in sensor data analysis coupled with an IoT or IIOT platform are key enablers for the deployment of more sensors for more applications.

John Blyler is a Design News senior editor, covering the electronics and advanced manufacturing spaces. With a BS in Engineering Physics and an MS in Electrical Engineering, he has years of hardware-software-network systems experience as an editor and engineer within the advanced manufacturing, IoT and semiconductor industries. John has co-authored books related to system engineering and electronics for IEEE, Wiley, and Elsevier.

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