This article is part of a series of articles realized in partnership with established experts from the IoT world. We have asked them to share their knowledge and best practices, giving you a step-by-step guide on how to successfully lead your IoT project, from its conception, to its life in the field. If you’d like to read more inspiring articles, just click here.
 

They have been around for longer than the Internet of things and even well before the Internet. They are discreet but at the same time, everywhere! Sensors are a key component of an IoT system and they act as its ears, eyes, nose, fingers, and even its taste buds. They gather data and provide the application with the information it needs to perform its duty. More recently, new technologies have given superpowers to sensors. They can now feel, think, analyze and even predict the future… well almost!

The advent of the Internet of Things has given sensors the leeway they needed to develop and numerous companies have hopped on the sensor train. With this plethora of choices, how do we choose the best sensor?

Gildas Henriet, Technical Marketing Manager and Tarik Souibes, EMEA Marketing Director at STMicroelectronics, one of the leading providers of high quality MEMS sensors for consumer and industrial applications, are giving us today, a few keys on how to approach this dilemma.
 

Gildas, Tarik, can you tell us in a few words what is the mission of STMicroelectronics and what differentiates you from your competitors?

STMicroelectronics has been known and recognized for its sensors, semiconductors and microsensors for about 20 years. We provide global solutions to our clients. Essentially we address 3 big domains: smart mobility, power & energy, and Internet of Things & 5G. Our products cover sensing solutions, processors, connectivity solutions, security solutions, power management solutions and everything around it: simulators, calculators, development tools, ecosystems, software and evaluation tools. Our solutions are proven in the field and can be personalized to suit any specific project. We have developed our own proprietary tools to allow for vertical integration. To go further, we created a global ecosystem that allows developers to connect their devices seamlessly and ensure that they interact securely with cloud applications and other devices. Our solutions are designed to enable the designer to focus on his project, without having to manage any infrastructure. In effect, it enables them to jump-start their sensor application development by providing tested platforms and open-source software applications.
 

What process do you apply to select the right sensor?

Our clients initially share with us their project objectives and their desired result. In accordance with the functionality that they wish to have in their finished product, we can then position our tools to allow the clients to evaluate —in a blink of an eye— the feasibility of their project and validate its concept. On this basis, the client can start developing. I dare say: “it’s as simple as that”!

We can then accompany the client with applicative assistance thanks to an online support facility but theoretically, with our products and tools, available online, the client can be self-sufficient, even if not an expert. Our tools —like the SensorTile.box— can be configured according to the level of knowledge that the client has of our products. This product is a small box in which we’ll find the majority of our sensors plus a processing block and connectivity. They are plugged on a PCB that can be powered with a USB rechargeable battery. The system comes replete with an Android or IOS application whose parameters can be set for one of our existing applications or a bespoke application. We really put ourselves in the shoes of our interlocutor to ensure everything is made easy for him and he can concentrate on the tasks that have real added value. With SensorTile.box, our goal is to allow electronics designers to very quickly prototype and test their ideas, so that they can find out immediately if their idea is viable or not, and then if they can push it forward.

There are more and more communities of developers today, including our own community, where developers can help each other and share recommendations. We gather our clients’ feedback and integrate them into our processes to develop new innovative functionalities and create new applicative supports that were lacking before, such as our resources library. Today, part of our R&D responsibility is to listen and engage with the community to increase customers’ proximity: the communities are exchanging good practices; tips, software, codes, … we see many people developing things on their own… so maintaining, listening, caring about our community is important, to arouse interest and help them discover the potential of our solutions.

In the IoT world, it is difficult to have all needed skills in-house. Even large corporations or industrial companies don’t have the full expertise portfolio available internally, so they need to create their own ecosystem as well.
 

What are the right questions to ask when choosing a sensor?

We can tell that the IoT is now a more mature domain in spirit, in conception and projects. When IoT started, we had no guarantee that a device would work. Today, people who come to see us have a project that is better thought than previously. The success rate of IoT projects is a lot better than it used to be. But this ecosystem we mentioned didn’t exist back then. It's now a lot easier to find the right hardware and the relevant documentation, but still, there remain a few questions one needs to ask oneself when choosing a sensor for an IoT solution:

1. Why do you want to install an IoT sensor? What are you trying to achieve?
   You need to think about the end result and establish goals before you start the implementation process. This will avoid wasting time and money on technologies you won’t need to collect data you won’t be using.
    
2. What functionalities do you need in your product?  
   The range of sensors is wide but a sensor corresponds to the functional need. There are some sensors that detect vibrations, motion, noise, light, pressure, temperature, humidity…  The type of sensors you use will be dictated by your objectives.
    
3. Do you need the sensor to integrate Artificial Intelligence?
   Edge computing is a growing trend of the IoT although at STMicroelectronics, we’ve had sensors that integrate AI natively for a while now. They are able to process the data directly at the sensor level and up to the micro-controller. The calculations are made locally which means that the process of sending to the cloud is more efficient. These solutions not only allow us to save energy —and therefore extend the lifetime of the device— but also to acquire measurements more regularly and analyze more parameters since we are able to multiply the number of sensors. For example, in the past, the only thing we could measure to predict failure was the temperature. Now, thanks to predictive maintenance,  we can analyze the noise (including ultrasonic), and the vibrations in addition to the temperature. The benefits in being able to predict when the failures may happen are huge.
    
4. In which environment will the sensor be deployed?
   Will it be exposed to humidity? Which range of temperature will it have to sustain?  Make sure you compare your needs with the sensor manufacturer's compatibility charts. Doing this will help you select the right sensor. Potentially adapt it to fit your needs, determine its expected lifetime, and choose the best emplacement in which to install it.
    
5. What degree of accuracy do you need?
   Accuracy will have impact on the data measured; for example, considering a drone, accuracy will enable to stabilize the engine with high stability. This could also be the case for a dead reckoning usage in urban canyon to provide to the driver trajectory of the vehicle despite loss of GNSS signal…
    
6. When and where will the sensors be installed?
   If your objective is to track pallets, you’ll need to think about how big they need to be to ensure that they are securely installed on the pallet without disturbing operations. You’ll also need to make sure the sensors are installed in locations that are the best for collecting data but that also won’t get in the way of the staff.
    
7. Can the sensor be recalibrated once installed in the field?
   Sensors are already calibrated when they come out of the factory and most of the time, this is enough for the whole products’ normal lifetime. However, it may happen that the sensors need to be recalibrated or replaced due to drift, quality or installation environment; that is for example the situation for a magnetometer used for a compass application as sources of magnetic perturbation are present in our environment. These costs are often overlooked, but can easily surpass the original purchase price if not considered at the beginning of a project. In the use case described above, this can be easily handled thanks to a software library that ST can provide but be aware that if the MCU does not have enough memory to run this library, the consequences may be dramatic.
    
8. Is your chosen sensor at the beginning or at the end of its life?  
   Think about the future to ensure that your solution will stay ahead of the curve from day 1. Make sure that you take into account the technological evolutions. It’s an important point as you could start with products that are already obsolete before you even commence the project which could reduce your device’s longevity or increase your Total Cost of Ownership if you need to replace the sensor because it is not supported anymore. At STMicroelectronics, we offer a 10 year lifetime minimum policy on all our industrial and automotive product line sensors. When possible, we make sure that each generation is compatible with the next one so they can be easily updated by the client, which ensures the longevity of their products. We can direct the client towards the best solution and share trends with them. Generally speaking, the new products perform more efficiently and may offer new features allowing them to implement more functionality. Beyond Edge computing and AI, the big trends on our market is low energy consuming mode, sleep mode, deep sleep mode, etc.… We want to be able to do more and more computing “locally”, at sensor level, put more and more intelligence… but these functions require energy and power, so we need to optimize the energy consumption to enable new functions at sensor level. We could save between 10 and 100 times the energy needed to power these functions. What does it enable? More frequent measurements, more frequent data acquisitions and multiple sensors connected to the solution. We can therefore monitor more parameters, acquire different types of data and in greater quantities. As a result, the prediction gets more precise. On a production line, for example, we can now monitor both the temperature AND the vibration levels in order to predict accurately when a machine will fail or need maintenance.
    
9. What are the requirements linked to industrialization?
   There is on one hand the technical knowledge of the device, and on the other hand requirements linked to the industrialization. The client might not have the full field of technical knowledge in which case we are able to recommend partners to accompany them.

    

If you had to give 3 bits of advice to someone choosing a sensor, what would they be?
 

• The sensor is an important choice because it governs other important decisions in the IoT stack. So make sure you ask yourself all the right questions —as mentioned above —to select the correct one. Then, test your sensors with your solution as promptly as you can to provide a proof of concept and make sure that the sensors capture what you need them to capture! Thanks to off-the-shelf solutions, you can validate your concept within a week. Don’t forget to test your product against the right range of temperatures. STMicroelectronics provides vertical integration so the sensor can be rapidly tested to make sure it works for your needs. Once it’s done you can personalize your solution to make sure it achieves its full potential. Keep in mind the SensorTile.box example.
   
• Don’t forget security!
  Security is key for any IoT device, and sensors are no exception. Since they collect the data that drive the entire solution, they play a vital role. Make sure your hardware offers built-in security features and can ensure the integrity of your data. This will be even more critical if your device is intended for use in sensitive areas.
   
• Surround yourself with solution providers that are enduring and recognized.
  Some providers offer exotic solutions, but these solutions often won’t stand the test of time, and it’s always risky to choose a technology that doesn’t combine performance AND longevity. Cost is often paramount in designing sensors, and in an effort to save money, the underlying hardware may lack built-in features found in higher-end solutions. We’ve often encountered situations where STMicroelectronics solutions were compared to cheaper competing ones but the solutions didn’t perform as well as ours or the competitor was unable to deliver the range of quantities whereas we can accompany any type of business, big or small. So choose carefully and look at the total cost of the whole solution. In the long run, you’ll see that performance and quality always wins!
   

Thank You Gildas, thank you Tarik!