Electronics & Scientific Guide, How To, Measuring & Testing

How to measure the complex networked modules of the IoT

The networked devices of the Internet of Things are made up of different components that need to work together smoothly. Which measuring devices are necessary, we show you in the post.

There are many ways to turn existing objects into intelligent networked devices using microprocessors, I / O buses, sensors, and transmitters. However, the possibilities are associated with certain technical challenges. How do you transform tools and machines that have not changed in form or function for decades, into electronic devices that are user-friendly, networked, and standards-compliant? How to make sure the devices developed in the lab work in the field?

An efficient process requires a good test and measurement strategy and the tools to make the right design decisions in time. An IoT developer faces six key challenges, with test and measurement as a key part of the project:

  • Wireless Module Selection: Due to the increasing variety of available wireless modules, the choice is difficult. Accurate test and measurement technology provide insights that go beyond the data in the datasheet and shows whether a module can meet the respective requirements.
  • Digital design and debugging: When system-level debugging is required, it must be checked to see if the module or subsystem cause the problem. With a mixed-domain debugging, the cause can be traced faster.
  • Maximize battery life: If every minute counts in battery life, then energy needs to be accurately modeled.
  • Certification to EMI and EMC: Manufacturers of IoT devices need to learn how to extend their product to wireless capabilities and how to test for emissions and compliance now and in the future.
  • Certification of Wireless Standards: New products must be qualified for the standard used. This is done regardless of whether it is WiFi, Bluetooth or ZigBee.
  • Interference with other devices: The 2.4 GHz frequency spectrum is very popular for low-cost, royalty-free applications. That’s why millions of transmitters are active in this frequency band. A license-free spectrum is therefore attractive. However, there is no protection against other devices that operate in the same frequency band or on the same channels.

IoT design teams are most likely to encounter difficulties in debugging, battery life optimization, and pre-compliance testing.

High-frequency design and successful debugging

It is common for radio components to be designed by very experienced high-frequency development engineers. However, there are now countless wireless modules that can be integrated into hardware without the developer having significant experience in high-frequency design. This multi-functionality of the modules and the ever lower costs undoubtedly help to drive the explosive growth of IoT devices.

Depending on the functionality of the device to be also developed digital and analog circuits must be integrated. It must also be ensured that the radio module works. Figure 1 shows a typical IoT device: a WiFi module and a DC power supply and IoT-specific hardware.

The graph shows several potential problem areas where testing and debugging can be as easy as possible. After switching on the device, the first question arises: does it send or not? If a signal is sent, then it must be checked whether the frequency is correct and whether the signal level and the linearity are correct. In the simplest case, a spectrum analyzer helps.

The meter not only shows if the signal is present but also measures frequency and level. It may be necessary to decode the signal or to extract digital data from the signal. In this case, a vector signal analyzer (VSA) is required. The radio module only transmits what it should.

The application-specific module in is the brain of the device – it is programmed to control all modules, including the radio module. If the module does not work as expected, check why it is. The radio module may receive the wrong control signals, or it may be due to faulty bus commands. Also, a problem with the power supply is conceivable.

To debug the high-frequency, analog, and digital parts of the design, an oscilloscope is needed. The device captures all necessary signals simultaneously in time (standard oscilloscope functionality) and frequency domain (traditional analyzer of spectrum functionality).

Modern mixed-domain oscilloscopes have a dedicated spectrum analyzer channel to capture all relevant signals simultaneously. The time correlation allows possible problems to be considered comprehensively. If the radio does not work as expected, the commands sent to the module via the control bus and, at the same time, the radio frequency signal can be monitored.

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