Today, the Internet of Things (IoT) connects all types of physical sensors more directly than ever, allowing them to send their data to virtual dashboards with almost no human interaction.
This is thanks to the latest advances in IoT technology, such as cellular IoT and LPWAN (Low Power Wide Area Network), which fundamentally change how sensors are used—from occasional measurements to continuous, real-time remote monitoring across multiple industrial and consumer applications.
That said, sensors are not entirely a new thing.
Sensors have primarily been used to measure variables in the real world, such as temperature or pressure, and early sensor devices can be traced back to 1500.
As pointed out in a blog post:
Temperature measurement has existed for a long time, dating back to around 150 AD. However, it is estimated that the true scientific development of thermometers only began in 1500. Over the years, different types of thermometers have been developed.
Humans have always felt the need to measure things faster, more accurately, and more effectively than ever before. This is our nature, and it is also the reason for the rise of IoT sensors.
Before the advent of the IoT, there were already many types of measuring devices on the market, including thermometers, magnetometers (with the compass being a notable example), altimeters, and so on.
This list is never-ending.
The sensors used in these devices are designed to detect, measure, and report one variable from the real world at a time. Their entire purpose is to help us understand the world around us in a measurable, universal way that “anyone” can comprehend.
Ever seen a pilot’s cockpit?
The pilot’s cockpit is filled with flight instruments, such as altimeters and fuel gauges. These dashboards are filled with flight instruments that report variable data from various types of sensors, such as fuel levels, system pressure, and more.
The goal of developing the next generation of IoT sensors is also similar—to aggregate their data using IoT modules and send it directly to IoT dashboards, making it faster and easier to make important decisions.
Additionally, predictive maintenance is one of the key areas where IoT sensors are expected to change the way manufacturing and industrial operations are conducted. Of course, other interesting IoT applications are also on the rise.
Below, we will look at 12 types of IoT sensors that are realizing these use cases, along with some examples of sensor devices from different manufacturers.
1. Pressure Sensors
Pressure sensors are devices used to measure the pressure of gases or liquids (the force required to prevent fluid expansion), and they come in various sizes and shapes, making them one of the most popular examples of IoT sensors.
There are different types of pressure sensors.
For instance, barometers, which are included in most weather stations, are designed to measure changes in atmospheric pressure.
Another example is gas pressure sensors, which are designed to monitor pressure changes in gases, especially in oil, energy, and utility applications.
While technically weighing sensors are not pressure sensors, they are, in fact, a variant of pressure sensors, and can serve as a preferred method when measuring weight (such as the weight of animals or the liquid level in tanks or silos).
These types of sensors form the backbone of our natural gas and energy infrastructure, as we would not be able to monitor system pressure without them. By connecting an IoT module to one of these sensors, your data can be displayed on a computer screen.
Examples of IoT pressure sensors:
NCD’s Long-Range Wireless Pressure Sensor (Industrial)
Omron’s E8PC (Industrial)
Omron’s E8PC Industrial IoT Pressure Sensor
2. Light Sensors
Light sensors, also known as photoelectric devices or photodetectors, are passive optoelectronic devices that convert light energy (photons) into electrical energy (electrons). In life, light sensors are far more common than you might think.
Like pressure sensors, light sensors can serve various purposes and are widely used for brightness control, security, and even agriculture.
In agriculture, measuring the light absorbed by the soil is crucial. Therefore, tracking changes in light using light sensors is very useful for weather monitoring and applications in agriculture.
Light sensors can also be a simpler, more cost-effective alternative to motion sensors, such as those used for presence detection in hotel rooms, warehouses, or hallways.
Smart light IoT sensors are designed for industrial and consumer use (Source: Enlighted)
Examples of IoT light sensors:
Smart Sensors from Enlighted (Consumer and Enterprise)
NCD’s Long-Range Ambient Light Sensor (Industrial)
3. Temperature and Humidity Sensors
Temperature and humidity sensors are as popular and widely used as the two sensors introduced above. Humidity is usually tracked alongside temperature, and they are bundled together in pre-fabricated IoT modules.
On one hand, temperature sensors measure the thermal energy of a source, and their purpose is to measure temperature changes. On the other hand, humidity sensors measure the amount of water vapor in various gases in the atmosphere.
Temperature monitoring is a common use case in industrial environments, where machines need to operate at a certain temperature for extended periods.
Common use cases for temperature and humidity sensors include:
Food Safety Compliance
Cold Chain Monitoring in Healthcare and Hospitality
Warehouse and Inventory Management
HVAC System Monitoring
Examples of IoT temperature and humidity sensors:
Laird’s Sentrius™ RS1xx (Industrial Grade)
Brandless DHT-22 2302 (DIY)
4. Gyroscopes and Accelerometers
Many people should already be familiar with gyroscopes and accelerometers. They are the sensors that allow your smartphone to sense whether it is in portrait or landscape mode, and they are widely used in mobile game design.
In IoT applications, these small sensors are as popular as the ones used in your phone. Even though they have differences, most accelerometer chips also include a gyroscope, so we will combine them into one section.
The differences between the two are as follows:
A gyroscope is a device that uses the Earth’s gravity to help determine direction. Its design includes a rotor, a freely rotating disk mounted on the axis of a larger, more stable wheel. When the axis rotates, the rotor remains stationary to indicate the pull of gravity at the center, thus indicating the downward direction.
An accelerometer is a compact device designed to measure non-gravitational acceleration. When the object it is integrated into goes from rest to any speed, the accelerometer is designed to respond to the vibrations related to that motion.
ADI’s ADXL335 Accelerometer
In IoT, accelerometers are at the core of vibration sensors, which can convert acceleration data into vibration frequency (i.e., converting Gs to Hz!), commonly used to detect abnormal operations of industrial machines.
Gyroscopes can be used to determine the direction of movement of GPS-tracked objects, as well as wind direction in weather and clean energy applications.
Examples of IoT gyroscopes and accelerometers:
Kionix’s KX Series Accelerometers (Industrial)
Analog Devices’ ADXL335 Accelerometer (DIY)
5. Proximity and Motion Sensors
As a very common device, proximity sensors are applied in countless IoT applications. Proximity sensors can detect the presence of nearby objects without any physical contact by emitting an electromagnetic field or a beam of electromagnetic radiation (like infrared) and looking for changes in the field.
Some of these devices are also referred to as distance sensors, which use ultrasound to measure the distance between themselves and the detected object.
Proximity sensors can be confused with motion sensors, but they are not the same thing. Proximity sensors can detect motion by measuring the distance to an object, while PIR (Passive Infrared) sensors are a great low-cost alternative specifically designed for motion detection, as their output is mostly binary: 1 or 0.
These sensors are typically used in motion detectors, which can be used for anything from turning on lights to alerting the police in case of suspicious movement.
Examples of IoT proximity and motion sensors:
Seeed’s Various Proximity Sensors (DIY and Modular)
NCD’s Long-Range Wireless Proximity and Light Sensors (Industrial)
6. Flow and Gas Sensors
Flow sensors are devices used to measure the flow or quantity of moving liquids or gases, and they are somewhat related to gas sensors, which are electronic devices used to detect and identify different types of gases.
Flow sensors include all types of devices used to measure liquid and gas flow. Use cases include industrial process monitoring, HVAC, and gas and water management applications.
Smart metering is one of the areas where flow sensors have the most impact. Here, ultrasonic flow meters pair with IoT modules to send data to remote locations.
With the emergence of cellular IoT technologies like NB-IoT and LTE-M, along with clear benefits for utility companies and end-users, flow, gas, and electric sensors are expected to see significant growth by 2025.
This clearly indicates a strong trend in smart metering and an overall increase in the use of these types of industrial use sensors.
From the perspective of gas sensors, these sensors were traditionally bulky devices until recently, when they turned into low-power adaptive devices to monitor air quality in local environments.
Examples of IoT gas and flow sensors:
Sensirion’s Various Flow Sensors (Industrial)
Spec Sensors’ Various Gas Sensors (DIY and Modular)
7. Sound Sensors
In contrast, sound sensors are not as widely used as other types of sensors, but due to their unique properties and interesting use cases, they are still worth mentioning.
First, what are sound sensors?
Sound sensors are defined as modules that detect sound waves by intensity and convert them into electrical signals. When the device detects a change in intensity, it can send data back to the dashboard.
Simple sound sensors like those provided by Seeed Studio are quite inexpensive and can help you figure out some different use cases. For example, detecting the presence of sound in an otherwise quiet room.
There are also some recorders that not only detect sound but also record it immediately when the intensity changes, which is particularly useful for security.
Finally, an advanced use case involves what is known as a sound/noise level meter; devices that assess noise across the frequency spectrum.
These allow for more complex environmental noise measurement applications.
Examples of IoT sound sensors:
SensorTeam’s SoundSensor (Building)
IoTsens’ Sound and Noise IoT Sensors (Smart City)
8. Humidity Sensors
Humidity sensors are key to recent agricultural developments, allowing farmers to continuously monitor soil health. Soil conditions change constantly throughout the growing season, and due to the latest developments in soil and water monitoring, key information is being obtained from real-time measurements in the fields, helping farmers make faster and more accurate crop production decisions.
Most humidity sensors are single-point, meaning they measure moisture in the soil at a single fixed location.
These sensors should be installed at multiple locations in crop fields to improve measurement accuracy.
Depth also plays an important role here, as the effects of irrigation may be stronger or weaker at different levels. Moisture sensors are often equipped with long probes that can penetrate the soil and measure moisture at different depths.
Humidity sensors are very important for use cases in smart agriculture (Source: Sensoterra)
Examples of IoT humidity sensors:
Sensoterra’s Wireless Soil Moisture Sensor (Agriculture)
NCD’s Long-Range IoT Soil Moisture Sensor (Agriculture)
9. Image Sensors
Sensors are devices that collect information about the physical world to provide a set of measurements that change over time. In the same logic, we can view cameras as two-dimensional optical/infrared sensors that provide a matrix of measurements that change over time.
Cameras are widely used as a sensing mechanism, from personnel counting applications to AI-driven pattern recognition.
For example, Asimetrix’s PigVision technology is a unique application: an image-based sensor that measures the weight of pigs in real time based on a trained AI model.
Sony also strongly supports image sensor technology in industrial, utility, and aerospace fields.
Sony’s Advanced Pregius Industrial IoT Image Sensor Technology
Examples of IoT image sensors:
OmniVision’s OS02F10 (Industrial)
Sony’s Pregius Series Image Sensors (Industrial)
10. Magnetic Sensors
Magnetic sensors are used in both consumer and industrial applications to detect large metal objects, such as cars, panels, and housings. These devices can detect changes and disturbances in the magnetic field, such as flux, intensity, and direction.
Crocus Technology’s CT8xx Series Magnetic IoT Sensors
There are typically three types of magnetic sensors used in IoT:
1. TMR (Tunnel Magnetoresistance) Sensors
2. Reed Switches
3. Hall Effect Sensors
TMR sensors are becoming increasingly popular for measuring mechanical displacement and motion in industrial, automotive (e.g., automated parking and self-driving cars), and consumer applications.
Reed switches are electrical switches operated by a magnetic field. These switches can be actuated by electromagnetic coils and are often used in security systems to control current and trigger actions when harmful visitors are detected.
Hall effect sensors are used to measure the strength of magnetic fields.
Examples of IoT magnetic sensors:
HyperTech’s Custom Magnetic Sensors (Asset Tracking)
Crocus Technology’s CT8xx Series (Energy Sector)
11. Air Quality Sensors
Although air quality and water quality are functions that are jointly used by several types of sensors, we believe they should each have their own category.
When we talk about air quality, the first thing that comes to mind is pollution. But how do we measure it? By using so-called particulate matter sensors. Depending on the size of the particles in the air, these sensors mainly include two types.
PM10
PM2.5
When the particles are larger (generally 10 micrometers, hence the name), the sensors that can detect the former are more common. Detecting fine particles that are 2.5 micrometers or smaller becomes increasingly difficult.
Industrial particulate matter sensors from manufacturers like Sensirion can detect these fine particles and help implement air quality systems.
As discussed in previous sections, gas sensors also play a huge role in identifying changes in the air, and they are often embedded alongside PM sensors.
Examples of IoT air quality sensors:
ams’ Various Air Quality Sensors (Industrial)
Environmental Meteorology PM2.5 Particulate Matter Monitor (Smart Home)
Air quality sensors can be used in both industrial and consumer environments (Source: Ambient Weather)
12. Water Quality Sensors
Water is something that most of us take for granted, but many people around the world do not have clear access to this vital resource. Even when they do, its quality may be poor or directly toxic.
This is where water quality sensors come into play.
Several variables can affect water quality, some of which can be physically measured by sensors, such as:
pH Sensors
Turbidity Sensors
ORP (Oxidation-Reduction Potential) Sensors
When used together, these sensors provide a complete picture of water quality. For example, the following is an introduction to pH from the US Geological Survey:
pH is a measure of the relative amounts of free hydrogen ions and hydroxide ions in water. Water with more free hydrogen ions is acidic, while water with more free hydroxide ions is basic, and pH is influenced by the chemicals in the water, making it an important indicator of chemical changes in water.
Based on this, pH sensors play a huge role in monitoring water quality by observing the alkalinity of the water. Turbidity sensors play a similar role by measuring the amount of light scattered by suspended solids in the water. The less light, the worse the water quality.
Finally, oxidation-reduction potential sensors can measure the ability of a solution to act as an oxidizing or reducing agent, and can be used to measure the oxidizing capability of chlorine in swimming pools.
Examples of IoT water quality sensors:
Georg Fischer’s Signet 2724-2726 (Industrial)
Libelium’s Waspmote Water Quality Module (Various)
These are the 12 types of sensors in the IoT world that deserve our attention.
Author: AGUSTIN PELAEZ
Translated by: XIAOXIAO
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