Why IoT Devices Need EMI Testing

According to IEEE, the basic definition of an IoT device can be summarized as any object that is assigned an IP address and can transmit data over a network. Therefore, IoT devices can be anything. In fact, the range of IoT devices is very broad, from low-cost consumer gadgets (like a Bluetooth enabled $5 key finder) to very advanced and complex sensor networks used in medical, manufacturing, transportation, and utilities. Most (but not all) IoT products have some form of wireless capability, and for many designers, RF components can be a stumbling block; some engineers do not take wireless and EMI testing seriously.

So what does this mean for IoT and IoT designers? There is no clear definition. Even IEEE states in the aforementioned white paper that the definition is “very vague”. The challenges faced by engineers developing a Bluetooth remote key are completely different from those faced by engineers designing industrial-grade sensors or life-saving medical devices. Similarly, they face completely different testing and measurement challenges.

A common question in the IoT field is whether RF testing is necessary. For many low-end projects, testing is often considered a low priority because designers use pre-certified wireless modules and have tight delivery schedules that require meeting short time-to-market demands. The cost of testing equipment that can complete the testing tasks is also a significant factor. Startups or small businesses generally do not have the financial resources to purchase vector signal analyzers or spectrum analyzers.

Another barrier is the lack of expertise to conduct RF testing, leading to some interesting workarounds.

I recently encountered a development team that was integrating WLAN functionality into an aviation dust counter. They chose a pre-certified WLAN module, and the entire project looked almost like a software project. When the software was nearly complete, the testing they did was just to see the Wi-Fi speed of the counter with a store-bought Wi-Fi router at different distances. While this approach might provide some insights into performance, it is a far cry from true characterization and optimization.

As in the above example, you can integrate wireless modules into new or existing designs to achieve acceptable functionality. This approach is feasible for cheap consumer products—especially if you lack RF expertise and testing equipment. This approach assumes everything goes as planned, which is no different from the vendor’s claims.

Is this how things evolve in actual electronic engineering?

This haphazard testing approach is not suitable for industrial-grade or medical devices, especially those involving critical missions/lives or that need to be installed in remote or hard-to-reach locations. In such cases, thorough and comprehensive testing is essential.

There is a strong relationship between testing and improving reliability and performance, even when using pre-certified components, because the RF environment can change significantly once these components are integrated into the final product. Using pre-certified modules with custom antennas may not provide optimal power transfer, but significant improvements can be realized after optimization with a vector network analyzer. Measuring and optimizing DC power efficiency is crucial for wearable devices and other battery-powered devices.

Testing also helps you discover issues in-depth and ensures that basic functionalities work correctly. Recently, I encountered a company that faced Bluetooth pairing issues and tried several expensive testing devices to test the transceiver. Finally, with a friend’s suggestion, they used a USB spectrum analyzer to capture the data in the air. By using analysis software to demodulate these data packets transmitted in the air, they quickly identified the root cause of the problem.

Using pre-certified RF modules does not exempt you from the requirement for consistency testing against electromagnetic interference/electromagnetic compatibility standards. Many IoT design teams believe that EMI testing is just a formality. Unfortunately, this assumption is fundamentally flawed: the costs of EMI testing and repeated circuit board rework can escalate quickly.

Recently, a Chinese testing company revealed that 90% of the products they tested did not pass the first test. Given that the costs of EMI consistency testing range from $5,000 to $50,000, it is absolutely reasonable to recommend conducting consistency testing in advance.

Figure: Conducting preliminary electromagnetic interference tests before bringing products to testing laboratories can save time and money and solve tricky problems.

The rise of IoT devices is changing the RF testing landscape. Testing is often either done very quickly or fails altogether. Unfortunately, those products that do not pass may find it difficult to ultimately meet the standards. For those in the testing and measurement industry, there is a belief that there needs to be a focus on providing more powerful, cost-effective instruments capable of handling projects such as evaluating wireless modules, basic debugging, performance optimization, and pre-consistency testing for electromagnetic interference. They also need to continue improving usability so that even RF novices can gain valuable insights.Pre-consistency testing for EMI and RF standard consistency testing needs to be automated and made traceable.

Disclaimer:This article is an original work by the author, and the content represents the author’s personal views. The Electronics Enthusiast Network reposts it only to convey a different perspective and does not represent the Electronics Enthusiast Network’s endorsement or support of that view. If there are any objections, please feel free to contact the Electronics Enthusiast Network.

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