Top 12 IoT sensors

Nowadays, sensors are seemingly everywhere: In our homes, on public roads, on our cars, in hospitals, and in some cases, even inside our own bodies. While sensors have already been around for many decades, with the first thermostat being introduced in the 1880s and the first infrared sensor being developed since the 1940s, IoT will drastically increase their usefulness across many industries. Sensors form the backbone of every thriving IoT environment.

In a nutshell, sensors are devices that detect changes in an environment. These changes can be measured through a variety of inputs, such as light, temperature, ionization, motion, pressure, etc. At a particular scale, some companies require hundreds or thousands of these sensors in order to benefit from large datasets that are used to make crucial, informative corporate decisions. By converting standalone sensors into IoT-enabled devices, their deployment becomes scalable, as they can be controlled and maintained remotely.

The most promising sensors for IoT

Literally, any type of sensor can be deployed as an IoT-enabled device. Below we will identify the most promising sensors, their functions, as well as their use-cases.

M2M vs IoT

The terms M2M and IoT are frequently used interchangeably. While they are closely related, there are distinct differences between the two. IoT relies on M2M, while M2M systems don’t need IoT to work.

Temperature sensors

Temperature sensors are one of the oldest types of sensors and have been deployed in a wide variety of devices. Now, with the emergence of IoT, they are as relevant as ever. While just a couple of years ago, when industrial IoT wasn’t as established yet, temperature sensors were mainly used for smart home purposes in refrigerators or A/C units, nowadays, they have found a new purpose in IoT applications such as manufacturing, agriculture, and health care.

In manufacturing, numerous machines require specific temperatures to operate seamlessly. Temperature sensors can detect first signs of overheating and, as such, lay the groundwork for “predictive maintenance”-functionalities.

There are several different types of temperature sensors:

Infrared sensors: These sensors read temperature by intercepting emitted infrared energy of the object and identifying its intensity. Infrared sensors however are limited to either liquid or solid objects. They are ineffective in measuring the temperature of transparent compounds, such as gases.

Thermocouples: These devices read temperature by measuring the change in voltage. The voltage output of the thermocouple rises alongside temperature.

Thermistors: Thermistors are one of the most commonly used temperature sensors. Thermistors are resistors—their resistance changes when the temperature changes. Recording the change in resistance thus allows for measuring changes in temperature accurately.

RTDs (Resistor temperature detectors): RTDs are closely related to thermistors; however, the major difference is that thermistors are made of semiconductor material, while RTDs are metallic. This means RTDs are particularly suitable for measuring a huge variation in temperature.

Semiconductors (IC): In these devices, the conductivity increases, and using the resistance attributes of semiconductor materials, they can read temperature digitally. These are particularly useful for low-temperature readings.

Proximity Sensors

Proximity sensors are devices that detect the presence of nearby objects and convert these into a binary signal that can be easily read without having to get in contact with that object.

In retail, proximity sensors have been proven particularly useful in motion detection and as so-called “beacons,” which means they can help identify a correlation between customer behavior and products they might be interested in. Thus customers can be immediately informed about discounts of products within their immediate vicinity. Another, already well-established use-case of proximity sensors is in the automotive industries. Most commonly in parking assistants, that alert you about certain objects when reversing. They are also increasingly used in autonomous vehicles where they feed the AI the information it needs to make the right decision.

The most commonly used proximity sensors are:

Inductive Sensors: These proximity sensors work through induction. Using an electromagnetic beam, they can detect nearby metallic objects without touching them. While they are limited to metallic objects, they are reliable, robust, and can operate at very high speeds.

Photoelectric Sensors: Photoelectric sensors consist of components that are sensitive to light. They use light beams to detect the absence or presence of objects. They are mostly used for long-distance sensing or for detecting non-metal objects.

Ultrasonic Sensors: Ultrasonic sensors function similar to radar, sonar, or lidar. They can detect not only the presence of objects but also measure their distance. They are particularly suitable for harsh, demanding conditions.

Capacitive Sensors: Non-contact capacitive sensors measure the changes in electrical capacitance. When two spaced-apart, conductive objects have a voltage difference; they respond differently; this is called capacitance.

Water quality sensors

The use-cases for water quality sensors extend far beyond swimming pools. Particularly in the utility sector, receiving reliable, live data about the water quality in water distribution systems is a crucial measure to prevent public health disasters.

These are the most common type of water quality sensors:

Conductivity Sensors: Conductivity measurements measure the ionic concentration of water solutions. Or in other words, how many dissolved compounds there are in a solution.

pH Sensors: pH sensors measure the pH level, which tells us how acidic or alkaline the water solution is.

Chlorine Residual Sensors: These sensors measure the chlorine content in water. Chlorine is commonly used as an effective disinfectant.

Turbidity Sensors: Turbidity sensors measure different kinds of solids in water. These are typically used in wastewater management.

Infrared Sensors

Infrared sensors can sense different features of their surroundings by emitting and detecting infrared radiation. As mentioned above, these types of sensors can also be used to measure temperature. Infrared sensors are used in many different IoT projects. In healthcare, for example, infrared sensors can help monitor blood flow and blood pressure with ease. Every television uses infrared sensors in order to interpret the signals sent by a remote control. Infrared is also used to detect art forgery, as they enable art historians to see hidden layers within a painting, which is crucial to determining whether the artwork has undergone a restoration process.

Pressure sensors

There are numerous devices that rely on liquid pressure or other forms of pressure. Thus if a company wants to monitor the health of their devices through IoT, there is a good chance they will need to incorporate IoT-enabled pressure sensors into their environment.

If there is any deviation from the typical pressure range, the IoT-gateway notifies the system administrator about the problem. Thus a subsequent system failure can be prevented. These sensors are particularly common in manufacturing, as well as water and heating system maintenance.

Chemical sensors

Chemical sensors are incredibly diverse. Thus they are also actively deployed in a diverse variety of industries. They detect changes to liquid or aerosols.

These sensors are most commonly used in industrial environmental monitoring to detect accidentally released harmful chemicals, explosive detection, radioactive detection, etc. They are also used by the pharmaceutical sector and pretty much all kinds of laboratories make use of several types of chemical sensors.

The most common chemical sensors:

  • Nondispersive infrared sensors
  • Potentiometric sensors
  • Fluorescent chloride sensors
  • Chemiresistors
  • Zinc oxide nanorod sensors
  • Electrochemical gas sensors
  • Chemical field-effect transistors
  • Hydrogen sulfide sensors
  • pH glass electrodes

Gas sensors

Gas sensors are closely related to chemical sensors but are dedicated to monitoring air quality and detecting changes in the presence of different types of gases. They are used in industries, such as agriculture, health care, manufacturing, and mining.

Some of the most commonly used gas sensors are:

  • Ozone monitors
  • Oxygen sensors
  • Nitrogen oxide sensors
  • Hygrometers
  • Hydrogen sensors
  • Gas detectors
  • Electrochemical gas sensors
  • Catalytic bead sensors
  • Carbon monoxide detectors
  • Carbon dioxide sensors
  • Breathalyzers
  • Air pollution sensors

Smoke sensors

These sensors detect the presence and level of gases and airborne particles. They are most commonly installed as a safety measure to detect fire danger and are also used by the manufacturing industry and in smart buildings. They also help protect people who work in particularly dangerous or fragile environments, such as laboratories or explosive factories. Smoke sensors either detect smoke physically, optically, or through a combination of both.

The most common smoke detectors are:

Photoelectric (optical) smoke sensors: These rely on light scattering in order to detect smoke.

Ionization (physical) smoke sensor: The sensors measure ionization of the air; if there is a change in ionization that is indicative of smoke, the ionization smoke sensor will alert the IoT system.

Level Sensors

Level sensors can sense the level of certain substances, such as powders, liquids, or fine granular objects. Numerous industries, such as utility, food, and beverage manufacturing, as well as manufacturing, rely on level sensors. Waste management systems use level sensors to control the level of waste in a dumpster.

There are two commonly used level sensors:

Continuous level Sensor: Continuous level sensors measure levels within a predetermined range and provide real-time level readings. These are the kind of sensors used to display the amount of fuel in a vehicle (i.e., the fuel level indicator on a car’s dashboard)

Point level sensors: These sensors are binary, which means they do not provide continuous readings, but rather trigger an alarm if the object is above or below the pre-programmed level.


As the name says, accelerometers can sense the acceleration of an object. However, they can also detect changes in gravity. Accelerometers are most commonly used in fleet management and smart pedometers.


Gyroscopic sensors sense angular velocity, which means they measure the speed a device moves around a particular axis. Their most prominent use-case is in the automotive industry, where they feed crucial information to electronic stability control features, such as anti-skid systems.

Optical Sensors

Optical sensors detect rays of lights. They have a massive variety of use-cases, and many optical sensors in-use today already function as IoT-enabled devices. In the automotive industry, self-driving cars use optical sensors to recognize signs, obstacles, and other objects. Optical sensors also play an important role in the quality control process of many manufacturers.