Series of Innovators: SPEC Sensors


SPEC Sensors was founded in 2012 in the USA (California) by Dr. Joseph Stetter and Ed Stetter. Their gas sensors, analog and digital, are one of a kind as the technology and hard work has allowed them to minimize the sensor size to only 20x20x3 mm in order for gas sensing to become a part of our everyday lives. The company has foreseen that sensors of all types are going to be integrated into smartphones and other wearable devices, becoming an integral part of our everyday lives and building the Internet of Things (IoT).

IoT low-cost sensors are in my DNA as I believe they will allow us to understand environmental issues otherwise, we would have dismissed or we would not be aware.

Let’s read together what they have to share with us and reach a conclusion at the end.


  • Tell us a bit about your motivation in developing air quality sensors?

We saw the need and opportunity for low cost electrochemical sensors with good performance – before SPEC, high performance sensors were too expensive and too big to enable new applications in wearables and distributed monitors. SPEC was born out of the research driven by Eco Sensors / KWJ Engineering, Inc. led by Dr. Joseph Stetter.  We were able to build SPEC Sensors using modern technology in a new high performance plastic package.

  • Tell us about the Digital Gas Sensors for IoT, why did you develop this type of sensors?

We designed the Digital Gas Sensors (DGS) to make it easy for engineers all over the world to incorporate gas sensing into projects. Our vision was to make gas sensing more accessible, and what we have seen is the DGS has become more than just a tool for engineers to add sensors to their products. The DGS has been used in volumes for projects and in universities and schools for teaching. It has become a product in and of itself, bringing high performance sensing to the broader community of makers, students and citizen scientists.

  • What is the difference between the Analog and the Digital sensors and which one should we choose in order to have more accurate measurements?

The Digital Gas Sensor has better performance, generally, than the Analog ULPSM. The analog module is a good starting point for those who can convert the analog signal to digital and to do the signal processing on their own. The Analog ULPSM is primarily designed for low power operation. The DGS uses the higher performance LMP91000 ASIC and has signal processing and temperature compensation on board. Both modules use the same sensor, highlighting the role that implementation plays in sensor performance. A sensor is only as good as its implementation. It is critical, especially for air quality measurements, to have a high performance, high resolution circuit with calibration, compensation, and proper sampling. Our app notes are a good starting place for directions on how to implement our sensors.   

Dr. Joseph Stetter’s answer: Digital sensors talk to computers and their output is a string of 0 and 1 bytes that represent the “analog” or continuous voltage that all sensors put out. The main job of a sensor is to respond to a stimulus [like the concentration of a molecule like Ozone or CO] with a voltage [typically] that represents that concentration. The digital world translates the voltage into a series of bytes [0,1] so that computers can operate on it. When analog is converted to digital, the whole world of computation and communication are opened to the sensor signal!

  • We desperately need reliable sensors for outdoor urban monitoring, which sensors will give us better results among your product range (NO2, O3, CO, H2S, SO2)?

While all our sensors perform well, we have seen the best results with our CO sensors in outdoor studies with a >90% correlation with high cost reference monitors and very little if any drift over time. Our O3 and NO2 sensors have also tested well with correlation >80%, but these are much more difficult to implement because of the nature of O3 and NO2 gas and its complication both in calibrating devices and compensation for various atmospheric conditions like temperature, pressure and relative humidity.

  • What, in your opinion, makes a good air quality sensor?

It is a combination of factors that produce a good air quality sensor.  If a sensor is high performance but too expensive to be deployed in adequate quantities, it is missing something. We think good air quality sensors have a combination of low cost, small size, stability, performance and affordability. In air quality, perhaps there is too much emphasis on absolute accuracy for distributed sensors, and more emphasis should be given to actionable data.DGS-xx hand

  • What are the biggest challenges for you in doing what you do as a company?

We have many challenges as a small business with limited resources. While supply chain is always a challenge at our size, our biggest problem is the diversity of applications and environments our sensors will see in the field. There are so many factors between the end of our production line and their placement in the field. We support our customers from design to product launch to ensure they see great performance in the field.

  • What differentiates your air quality sensors from other manufactures?

We focus on air quality sensors such as CO, O3, NO2, and our priority is on making them low cost and low power.  We also do this without sacrificing performance and we provide exceptional costumer service.

  • In your experience, are people in your country aware of the air pollution crisis?

This varies based on location as we have a very diverse population. People who live in cities are much more aware of air pollution and the crisis it is causing than those living in the countryside.   

  • How do you see the direction of the future when it comes to air pollution?

People I find care about air pollution, but they feel powerless to stop it or change it.  I also believe in the power of technology.  As monitors and sensors develop will laws and public policy that improve environmental conditions follow? When people are informed and have access to sensors to measure their environment, they will drive change in legislation and demand products that are better for the environment. We believe information is power and change is coming with sensors playing a key role.

  • Any final comments or upcoming new sensor?

Our most recent product launch, SPARROW CO & Air Quality Monitor, by our partner company Eco Sensors, contains a SPEC CO sensor.  This is currently a single gas monitor that connects to a smart phone app, and shows the potential for air quality monitoring and personal safety. We are proud to bring this device to the market to showcase how very small, low cost sensors can improve people’s lives and put environmental monitoring in everyone’s hands.


All in all, I love their honesty, and I think they have a clear vision of what they want to develop and deliver to the world. I agree with their statement that sometimes it is given too much emphasis on absolute accuracy for distributed sensors, and more emphasis should be given to actionable data. Among other sensors, I have tried their CO sensor, it is true, it is very stable and accurate, which makes it perfect for portable/wearable devices. Thanks to their passion, people all over the world will be able to see the air pollutants and take action by demanding political changes.

Coming up a review of their all-new SPARROW CO & Air Quality Monitor, stay tuned.


One thought on “Series of Innovators: SPEC Sensors

  1. Thank you for that very informative article!

    We are currently looking into O3 and NOx sensors (for a specially designed new outdoor unit) and compared to PM2.5 sensors it is much harder to find accurate and reliable modules.

    We will have a closer look at the SPEC sensors.

    Liked by 1 person

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