Types of Sensors in IoT

IoT or the Internet of Things is the newest trend that’s been used for many products and appliances these days. While it’s easy to dismiss it as the newest fad, IoT devices do have a huge potential in disrupting and revolutionizing our lives and workflows and is indeed a technology that we need to pay attention to.

An IoT device is a physical object with sensors/actuators, processors, software and common communication ability that allows it to send and exchange information with other IoT devices, forming a collective network of smart systems. These can then be used to set routines, reminders, and alerts and be used to completely automate current workflows effectively.

IoT devices can encompass many functions and features and can be broadly divided into based on what type of device it is - whether it is a 

1. Sensor device - like temperature, humidity, pressure, light, distance
2. Actuator device - fans, blinds, motors, pumps, valves
3. Communication device - hubs for Zigbee, Z-wave, Matter, WiFi router, etc

For this blog, we will primarily be focusing on Sensor devices and different types of sensors in IoT

What are Sensors?

Sensors are devices that provide an output signal based on measuring an environmental phenomenon such as measuring temperature, humidity, pressure, altitude, ambient light, distance etc.

These devices are used to give quantitative and qualitative measurements of an environmental factor for the purposes of monitoring data to either record or take action.

For example, a temperature sensor can be used to monitor the ambient temperature. Based on the temperature sensor’s measurement and output, heating or cooling can be enabled to bring the ambient temperature of the room to the optimal temperature

Sensors in IoT

Sensors have been around for decades being used in many different applications. But recently, with the advent of IoT sensors, today must encompass the ability to process its data, communicate with other sensors and platforms, forming a crucial part in the entire IoT ecosystem

Classification of Sensors

Due to the sheer number of sensors available, for simplification sensors are divided into 5 core classifications depending on how they work

1. Active and Passive Sensors
2. Contact and Non-contact Sensors
3. Absolute and relative sensors
4. Analog and Digital Sensors
5. Miscellaneous Sensors

1. Active and Passive Sensors

Active Sensors are sensors that require a dedicated external power supply in order to function. Examples include GPS and ultrasonic sensors. 

Passive sensors on the other hand do not require any external supply and can receive enough electrical signal from the environment to function. Examples include thermal sensors, NFC tags, etc

2. Contact and Non-contact Sensors

Contact sensors are sensors that require physical contact with the environmental stimulus the sensor is measuring. Examples include touch sensors, temperature sensors, strain gauges, etc

Non-contact sensors are sensors that do not require direct contact with the environmental stimulus it measures. Examples include optical sensors, magnetic sensors, infrared thermometers, etc

3. Absolute and Relative Sensors

Absolute sensors, as its name suggests, provide an absolute reading of the stimulus. For example, thermistors always give out the absolute temperature readings

Relative sensors provide measurements relative to something that is either fixed or variable. Thermocouple is an example of a relative sensor, where the temperature difference is measured as opposed to direct measurement

4. Analog and Digital Sensors

Analog sensors produce a continuous output signal proportional to the measurement. Examples include thermometers, LDR, pressure sensors etc

Digital sensors are sensors that convert the measurement into a digital signal. Examples include Inertial Measurement Units, ultrasonic sensors, etc

5. Miscellaneous Sensors

There are many more types of sensors that may not necessarily fit into the above categories. Those sensors will be classified as miscellaneous sensors and these include biological, chemical, radioactive sensors, etc

Top 8 IoT Sensor Types

1. Temperature Sensor

Temperature sensors are used to measure the temperature of the ambient room. Temperature sensors come in different variants each working on different principles ideal for each use case, depending on the placement (indoor or outdoor), expected temperature range, temperature variations, size, etc

Examples: Thermistors, thermocouples, RTD, mercury thermometers, pyrometers, etc

2. Distance Sensors

Distance sensors are sensors that measure the distance between the sensor and any objects. These sensors can also work on many different principles and the type of sensor is chosen based on range, accuracy, durability, etc

Examples: Infrared, Radar, Ultrasonic, Lidar, etc

3. Light Sensors

Light sensors are sensors used to measure the intensity of ambient light. Different types of light sensors are used based on the variations of light intensity it is required to measure

Examples: LDR (light dependant resistors), photodiode, OPT3001

4. Optical Sensors

Optical Sensors are sensors designed to measure a particular attribute by making use of a light source and light sensor. Optical sensors are used in encoders to measure rotational speed by calculating the number of times the light source has been blocked and unblocked by the slits present on the wheel.

5. Inertial Measurement Units

Inertial Measurement Units usually consist of two or more sensors designed to detect and record motion and orientation. These include an accelerometer and gyroscope, the former being able to measure the acceleration (and hence orientation based on Earth’s gravity) and the latter measuring angular position. It is common to see a Magnetometer and pressure sensor also couple with IMU to further measure the direction like a compass and measure altitude respectively

6. Environmental Sensors

These sensors include pressure, temperature, humidity, moisture, gas sensors, sound sensors etc all designed exclusively to measure a particular physical attribute in the surrounding environment.

Conclusion

In conclusion, many types of sensors are available on the market designed to accurately measure and report various environmental stimuli. These sensors can be combined with a processor and a standard communication protocol to turn the device into a smart device or IoT product, turning into a collective, intelligent node in a wider network of smart devices.

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