Sensors may be “at the heart” of the Internet of Things fundamentally. But, in practice, they are usually detecting events or changes in the physical environment in remote locations (“the edge”) dispersed from the point of data ingestion and processing (“the cloud”). IoT discussions sometimes refer to sensors as the “things” when they are actually a part of something larger called a device, node, or endpoint. Other components handle functions inside the same enclosure, such as network communication, power management, and energy storage.
Among the many enablers for the rapid growth of IoT are the improvements in sensor technology. The industry has been continuously innovating to reduce size, power, reliability, and cost. A simple temperature sensor, for example, is available for around one US dollar, even in small quantities.
When making selections, besides price, there are often features or specifications to consider. Looking at the same example of a low-cost temperature sensor, some of the products’ differences include accuracy, operating temperature range, and power consumption. Other popular sensors may require a more detailed assessment to determine fitness for a particular use case.
In general, accelerometers measure the rate of velocity change, but different accelerometer technologies are available, including variable capacitance, piezoelectric, and piezoresistive. Each is more suitable for specific applications, so when looking at solutions for tilt, impact, motion, or vibration measurement, it’s essential to select the most appropriate type. Some other considerations are acceleration range (the lowest and highest acceleration measurable), sensitivity, and accuracy within a particular technology.
For some use cases, like measuring the level in a tank or bin, the potential choices use entirely different devices. Laser, radar, and ultrasonic units can monitor levels, deriving the distance from the device to the material using “time of flight” (the amount of time for a pulse to travel from the device to the surface and back). The decision criteria for selecting from these solutions include price, range, accuracy, and suitability for environmental conditions.
These are just a small set of examples of the choices available, depending on the need. Many other IoT applications require sensors for humidity, air quality, air pressure, flow, to name just a few. It is essential to clearly define what you want to measure and qualify all the criteria to make the appropriate selection. Most of these evaluation processes will require some substantial expertise to do it well.
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