4.b) Explain the major factors influencing the choice of sensors in IoT-based sensing solutions.
Answer:
The following major factors influence the choice of sensors in IoT-based sensing solutions:
- sensing range
- accuracy and precision
- energy
- device size
These factors are discussed as follows:
1.Sensing Range
- The sensing range of a sensor node defines the detection fidelity of that node.
- Typical approaches to optimize the sensing range in deployments include fixed kcoverage and dynamic k-coverage.
- A lifelong fixed k-coverage tends to usher in redundancy as it requires a large number of sensor nodes, the sensing range of some of which may also overlap. In contrast, dynamic coverage incorporates mobile sensor nodes post detection of an event, which, however, is a costly solution and may not be deployable in all operational areas and terrains.
- Additionally, the sensing range of a sensor may also be used to signify the upper and lower bounds of a sensor’s measurement range.
- For example, a proximity sensor has a typical sensing range of a couple of meters. In contrast, a camera has a sensing range varying between tens of meters to hundreds of meters.
- As the complexity of the sensor and its sensing range goes up, its cost significantly increases.
2. Accuracy and Precision
- The accuracy and precision of measurements provided by a sensor are critical in deciding the operations of specific functional processes.
- Typically, off-the-shelf consumer sensors are low on requirements and often very cheap. However, their performance is limited to regular application domains.
- For example, a standard temperature sensor can be easily integrated with conventional components for hobby projects and day-to-day applications, but it is not suitable for industrial processes. Regular temperature sensors have a very low-temperature sensing range, as well as relatively low accuracy and precision. The use of these sensors in industrial applications, where a precision of up to 3–4 decimal places is required, cannot be facilitated by these sensors.
- Industrial sensors are typically very sophisticated, and as a result, very costly. However, these industrial sensors have very high accuracy and precision score, even under harsh operating conditions.
3. Energy
- The energy consumed by a sensing solution is crucial to determine the lifetime of that solution and the estimated cost of its deployment.
- If the sensor or the sensor node is so energy inefficient that it requires replenishment of its energy sources quite frequently, the effort in maintaining the solution and its cost goes up; whereas its deployment feasibility goes down.
- Consider a scenario where sensor nodes are deployed on the top of glaciers. Once deployed, access to these nodes is not possible. If the energy requirements of the sensor nodes are too high, such a deployment will not last long, and the solution will be highly infeasible as charging or changing of the energy sources of these sensor nodes is not an option.
4. Device Size
- Modern-day IoT applications have a wide penetration in all domains of life. Most of the applications of IoT require sensing solutions which are so small that they do not hinder any of the regular activities that were possible before the sensor node deployment was carried out.
- Larger the size of a sensor node, larger is the obstruction caused by it, higher is the cost and energy requirements, and lesser is its demand for the bulk of the IoT applications.
- Consider a simple human activity detector. If the detection unit is too large to be carried or too bulky to cause hindrance to regular normal movements, the demand for this solution would be low. It is because of this that the onset of wearables took off so strongly. The wearable sensors are highly energy- efficient, small in size, and almost part of the wearer’s regular wardrobe.