15 Types of IoT Sensors Widely Used Today

What is an IoT Sensor?

Iot sensor is an electronic module that senses, collects and transits surrounding environment data to centralized systems through the gateway. Systems like weather stations, Dehumidifiers, Smart Irrigation Systems, Smart Traffic Lights, Smart Doorbells, Tire Pressure Monitoring Systems, etc, are integrated with these sensors gather data like temperature, humidity, water levels, traffic patterns, motion, pressure, etc related to surrounding environment where it is deployed and transmit collected data via gateways like Wi-Fi, Bluetooth, or other wireless communication protocols to centralized systems like LANs, WANs, Local databases, and cloud-based systems where these data are shared, processed, and stored, ensuring efficient and seamless data management across various platforms​​.

For example, in Apple Watch, which features various sensors to monitor vital signs, sleep patterns, and physical activity in real-time. It includes an electrical heart sensor, optical heat sensor, accelerometer, gyroscope, and temperature sensor, among others. The tiny computer chip leverages these sensors to gather your information and provide insights about your health to help you make informed decisions and achieve your wellness goals. The seamless integration of IoT sensors in any smart IoT device and its ability to collect and transmit data has placed it at the core of application development.

Types of IoT Sensors

Among various IoT sensors available today that collect, process, analyze, and transit different types od surrounding data here are the 15 most common types of IoT Sensors:

1. 1. Temperature Sensors
2. 2. Proximity Sensors
3. 3. Pressure Sensors
4. 4. Water Quality Sensors
5. 5. Chemical Sensors
6. 6. Gas Sensors
7. 7. Smoke Sensors
8. 8. IR Sensors
9. 9. Level Sensors
10. 10. Image Sensors
11. 11. Motion Detection Sensors
12. 12. Accelerometer Sensors
13. 13. Gyroscope Sensors
14. 14. Humidity Sensors
15. 15. Optical Sensors

1. Temperature Sensors

A temperature sensor is a device that detects and measures the amount of heat energy/temperature from a particular source and converts the data for a device or user in an understandable and readable format.

Based on the principle of voltage across the diode terminals, a temperature sensor collects data regarding the change in temperature and converts it into electrical signals. This converted data is displayed in readable units of temperature, such as Celcius and Fahrenheit.

In Smart Thermostats like Nest Thermostats, temperature sensors continuously detect and monitor the real-time room temperature. The collected data is shared with a central system, which adjusts the heating and cooling conditions of the room according to the user’s pre-set preference. This real-time temperature adjustment enable performance improvement and allows efficient use of energy. It also help prevent uncomfortable temperature change.

Similarly, temperature sensors are very beneficial for agriculture in monitoring and managing environmental conditions related to specific crops. They are installed inside a greenhouse or indoor farm where they continuously monitor the temperature and ensure specific crops get their ideal growing temperature. These sensors gather real-time data, helping farmers adjust the heating and cooling system necessary for optimal growing conditions for crops.

Other areas of use include cold chain management in food safety, weather stations, engine temperature monitoring in the automotive industry, fire detection systems in fire alarms, pharmaceutical storage facilities, and HVAC (Heating, Ventilation, and Air Conditioning) Systems.

Sub-categories of Temperature Sensors:

• Thermocouples: These are voltage devices that indicate temperature measuring with a change in voltage. As the temperature goes up, the output voltage of the thermocouple rises.
• Resistor Temperature Detectors (RTDs): The device’s resistance is directly proportional to the temperature, increasing positively when the temperature rises and resistance increases.
• Thermistors: A temperature-sensitive resistor changes its physical resistance with the temperature change.
• IC (Semiconductor): These are linear devices in which the conductivity of the semiconductor increases linearly. They take advantage of the variable resistance properties of semiconductor materials. They can provide a direct temperature reading in digital form, especially at low temperatures.
• Infrared Sensors: It detects temperature by intercepting a portion of emitted infrared energy of the object or substance and sensing its intensity; they can be used to measure the temperature of solids and liquids only; not possible to use it on gasses because of their transparent nature.

2. Proximity Sensors

Proximity sensors are devices that detect the presence or absence of a nearby object or properties of that object and convert it into a signal that can be easily read by a user or a simple electronic instrument without getting in contact with them.

A proximity sensor discharges an electromagnetic field or a beam of light as a signal that detects changes when it is reflected or interrupted by an object. Based on the changes and collected data, it determines the distance of the object. This information either triggers an action or gives feedback to the user via different apps.

Proximity sensors are used mainly in the retail industry. They can detect motion and the correlation between a customer and a product they might be interested in. Users are immediately notified of discounts and special offers on nearby products.

Another significant usage is seen in the parking assistance system for vehicles. When you are reversing your car, the proximity sensor emits sound waves to measure the distance of nearby objects and notify you about an obstacle, helping you to park safely.

Other uses include automated door systems, smartphones, aerospace, elevator systems, and industrial automation.

Sub-categories of Proximity Sensors:

• Inductive Sensors: Inductive proximity sensors are used for non-contact detection to find the presence of metallic objects using electromagnetic fields or a beam of electromagnetic radiation. It can operate at higher speeds than mechanical switches and also seems more reliable because of its robustness.
• Capacitive Sensors: Capacitive proximity sensors can detect both metallic and non-metallic targets. Nearly all other materials are dielectric, different from air. It can sense very small objects through a large portion of the target. So, generally used in complex and complicated applications.
• Photoelectric Sensors: A photoelectric sensor is made up of light-sensitive parts and uses a beam of light to detect the presence or absence of an object. It is an ideal alternative to inductive sensors and is used for long-distance sensing or to sense non-metal things.
• Ultrasonic Sensors: Similar to radar or sonar, ultrasonic sensors detect the presence or measure the distance of targets. They are reliable solutions for harsh and demanding conditions.

3. Pressure Sensors

A pressure sensor is a device that senses pressure exerted by a liquid or gas on a surface and converts it into an electric signal. Here, the amount depends upon the level of pressure applied.

Applications use different pressure sensing methods like piezoelectric, capacitive, piezoresistive, or optical. Piezoelectric sensors convert pressure into an electrical charge, capacitive sensors detect changes in capacitance and amplify the information via some circuitry, piezoresistive resist under stress, leading to a change in its electric resistance, while optical devices notice variations of light intensity or wavelength due to deformation induced by loads.

When a pressure fluctuation is detected, the pressure sensor measures its consequent physical alteration. After the completion of measurement in physical change, the data is transformed into electrical signals which are then displayed into readable format.

Deployment of these sensors is very useful in the manufacturing and maintenance of whole water systems and heating systems, as it is easy to detect any fluctuation or drops in pressure.

Other application areas encompass:

• Medical devices to measure blood pressure and respiratory pressure
• Aerospace applications to measure cabin pressure and altitude pressure
• Weather stations use it to measure atmospheric pressure
• Marine industry uses it in submarines and underwater equipment to calculate water pressure

4. Water Quality Sensors

Water quality sensors detect water quality and ion monitoring, primarily in water distribution systems, by measuring different parameters. These parameters include turbidity, pH, conductivity, dissolved oxygen, temperature, and presence of ions or chemicals.

Water quality sensors use sensing technologies like electromechanical, thermal, and optical methods, when they are in direct contact with water. These sensors translate the chemical, biological, and physical properties of water into an electrical signal. These signals get processed and are sent to data loggers, controllers, or any remote monitoring system that controls the water quality.

The water sensors are profoundly used in various sectors like drinking water treatment plants, wastewater treatment, swimming pools, industrial waste management, aquaculture, and agriculture.

Most common types of water sensors in use:

• Chlorine Residual Sensor: It measures chlorine residual (i.e., free chlorine, monochloramine & total chlorine) in water and is most widely used as a disinfectant because of its efficiency.
• Total Organic Carbon (TOC) Sensor: The TOC sensor measures organic elements in water.
• Turbidity Sensor: Turbidity sensors measure suspended solids in water; they are typically used in river and stream gaging, wastewater, and effluent measurement.
• Conductivity Sensor: Conductivity measurements are carried out in industrial processes primarily to obtain information on total ionic concentrations (i.e., dissolved compounds) in water solutions.
• pH Sensor: It measures the pH level in the dissolved water, indicating the level of acidic or basic (alkaline) water contains.
• Oxygen-Reduction Potential (ORP) Sensor: The ORP measurement provides insights into the level of oxidation/reduction reactions occurring in the solution.

5. Chemical Sensors

Chemical sensors are devices that detect, measure, and convert the chemical substance concentration of a specific analyte into electroanalytical signals.

Chemical sensors are based on different principles, covering electrochemical and optical methods right through to mass-sensitive processes. Three types of sensors, such as electrochemical, measure changes in electrical properties; optical sensors are based on the detection of light property variations; and mass-sensitive sensors measure alterations in weight captured from sensed objects.

Whenever the target chemical comes in contact with the sensitive layer of the sensor, it changes the properties (electrical conductivity, light absorption, or mass) of the sensor. This modification is transduced into an electrical signal that can be processed to identify the kind and concentration of the chemical substance.

The primary use cases of chemical sensors can be found in Industrial environmental monitoring and process control, intentionally or accidentally released harmful chemical detection, explosive and radioactive detection, recycling processes on Space Station, pharma industries and laboratories, etc. Other areas of use are medical diagnostics, food and beverage industry, agriculture, breath analysis, fire detection systems, and water quality analysis.

Most common types of chemical sensors in use:

• Chemical field-effect transistor
• Chemiresistor
• Electrochemical gas sensor
• Fluorescent chloride sensor
• Hydrogen sulfide sensor
• Nondispersive infrared sensor
• pH glass electrode
• Potentiometric sensor
• Zinc oxide nanorod sensor

6. Gas Sensors

Gas sensors are similar to chemical ones but are specifically used to monitor air quality changes and detect the concentration of various gasses in the air. They determine the differences in the physical or chemical characteristics of a sensing material when exposed to certain gas/gasses.

There are many types of sensors available, including pellistor (catalytic bead), infrared, electrochemical, and semiconductor. Electrochemical cells generate current through a chemical reaction that changes in gas concentration; semiconductor devices measure changes in electrical conductivity proportional to gas adsorption; infrared mechanisms measure optical absorbance of infrared light by gas; catalytic combustion sensors detect heat generation during gas oxidation. The presence of the target gas modifies one or more measurable characteristics such as electrical conductivity and/or resistance. This change is translated to an electric signal that, when processed, produces the gas concentration.

Like chemical sensors, they are used in numerous industries such as manufacturing, agriculture, and health and used for air quality monitoring, detection of toxic or combustible gas, hazardous gas monitoring in coal mines, oil and gas industries, chemical laboratory research, manufacturing – paints, plastics, rubber, pharmaceutical and petrochemical, etc.

Following are some common Gas sensors:

• Carbon dioxide sensor
• Breathalyzer
• Carbon monoxide detector
• Catalytic bead sensor
• Hydrogen sensor
• Air pollution sensor
• Nitrogen oxide sensor
• Oxygen sensor
• Ozone monitor
• Electrochemical gas sensor
• Gas detector
• Hygrometer

7. Smoke Sensors

A smoke detector, also known as a smoke sensor, is a device that senses the presence of fire. The base mounts on the ceiling detect smoke particles in its proximity and sets off an alarm to alert occupants. These sensors use different mechanisms to detect the presence of smoke particles, such as Ionization Smoke Sensors and Photoelectric Smoke Sensors.

Smoke sensors are extensively used by the manufacturing industry, HVAC, buildings, and accommodation infra to detect fire and gas incidents. The system is much more effective than the older ones, protecting people working in dangerous environments.

Common Types of Smoke Sensors

Smoke sensors detect the presence of Smoke, Gases, and Flames surrounding their field. It can be seen optically by the physical process or by using both methods.

• Optical smoke sensor (Photoelectric): Optical smoke sensor uses the light scatter principle trigger to occupants.
• Ionization smoke sensor: This smoke sensor works on the principle of ionization, a kind of chemistry that detects molecules that cause a trigger alarm.

8. IR Sensors

An infrared sensor is a device that is used to detect specific characteristics of its surroundings by either emitting or detecting infrared radiation. It is also capable of measuring the heat emitted by objects. It converts the infrared radiation into an electrical signal which is processed to detect the presence, motion, or temperature of objects.

Active and passive IR sensors are two types of IR sensors. Active sensors emit infrared and detect the reflection from objects, while passive sensors detect natural infrared emitted by objects. These sensors collect data based on detected infrared change and use it to compute the distance, presence, and temperature of objects.

Their use is common, especially in healthcare, as they simplify monitoring blood flow and blood pressure. They are even used in regular intelligent devices such as smartwatches and smartphones.

Other everyday uses include home appliances & remote control, breath analysis, Infrared vision (i.e., visualize heat leaks in electronics, monitor blood flow, art historians to see under layers of paint), wearable electronics, optical communication, non-contact based temperature measurements, automotive blind-angle detection.

Their usage does not end there; they are also an excellent tool for ensuring high-level security in your home. Also, their application includes environment checks, as they can detect various chemicals and heat leaks.

9. Level Sensors

A level sensor is used to determine the level or amount of fluids, liquids, or other substances that flow in an open or closed system.

There are a variety of principles that level sensors follow, including ultrasonic waves for emitting sound waves and measuring the time it takes to return with echo; capacitive detection, which uses changes in capacitance from sensing material properties; radar by utilizing microwave pulses as a distance gauge; hydrostatic pressure or liquid pressure at varying depths; and optical methods through light-operated devices detecting presence. Whether in direct contact with the material or using non-contact methods, these sensors convert measurements into electrical signals. The data is then used for monitoring, control, or safety purposes.

They are primarily known for measuring fuel levels but are also used in businesses that work with liquid materials. For example, the recycling industry and the juice and alcohol industry rely on these sensors to measure the number of liquid assets in their possession.

The best use cases of the level sensor are fuel gauging and liquid levels in open or closed containers, sea level monitoring and tsunami warning, water reservoirs, medical equipment, compressors, hydraulic reservoirs, machine tools, beverage and pharmaceutical processing, and high—or low-level detection.

This helps streamline their businesses better, as sensors collect all the critical data at all times. Using these sensors, any product manager can precisely see how much liquid is ready to be distributed and whether the manufacturing should be stepped up.

There are two basic level measurement types:

• Point level sensors: Point level sensors usually detect a specific level and respond to the user if the sensing object is above or below that level. It is integrated into a single device to get an alarm or trigger
• Continuous level Sensor: Continuous level sensors measure liquid or dry material levels within a specified range and provide outputs that continuously indicate the status. The best example is the vehicle’s fuel level display.

10. Image Sensors

Image sensors convert optical images into electronic signals for displaying or storing files electronically.

An image sensor is an array of photodetectors (pixels) that transform radiation into measurable units. Charges proportional to light intensity are generated by the photodetectors when hit by light. That charge is converted into a voltage signal and eventually processed by an analog-to-digital converter (ADC) to produce the resulting digital picture. The image processing algorithms are used to manipulate and interpret the digital data afterward.

The primary use of image sensors is in digital cameras & modules, medical imaging and night vision equipment, thermal imaging devices, radar, sonar, media houses, and Biometric & IRIS devices.

Two main types of sensors are used:

• CCD (charge-coupled device), and
• CMOS (complementary metal-oxide semiconductor) imagers.

Although each type of sensor in IoT uses different technology to capture images, both CCD and CMOS imagers use metal-oxide semiconductors, having the same degree of sensitivity to light and no inherent quality difference

An average consumer would think that this is a regular camera. Still, even though this is not far from the truth, image sensors are connected to a wide range of devices, improving their functionality.

One of the best-known uses is the car industry, in which imagery plays a very important role. An automotive software development company would heavily rely on it to bring automation. With these sensors, the system can recognize signs, obstacles, and many other things that a driver would generally notice on the road. They play a very important role in the IoT industry, as they directly affect the progress of driverless cars.

They are also implemented in improved security systems, where images help capture details about the perpetrator.

In the retail industry, these sensors gather customer data, helping businesses gain a better insight into who is visiting their store. Race, gender, and age are only some of the functional parameters that retail owners gain by using these IoT sensors.

11. Motion Detection Sensors

A motion detector is an electronic device that is used to detect the physical movement (motion) in a given area, and it transforms motion into an electric signal. This includes the motion of any object or motion of human beings.

Several motion sensors are used to detect motion, including microwave, camera-based, passive infrared, and ultrasonic sensors. These sensors can monitor changes in infrared radiation, sound waves, or electromagnetic fields. They process and convert physical changes into electrical signals, which generate alerts when they detect the presence of a body or object.

Motion detection plays a vital role in the security industry. Businesses utilize these different sensor types in areas where no movement should be detected at all times, and it is easy to notice anybody’s presence with these sensors installed.

An IoT application development company will use these sensors primarily for intrusion detection systems, automatic door control, boom barriers, smart cameras (i.e., motion-based capture/video recording), toll plazas, automatic parking systems, automated sinks/toilet flushers, hand dryers, energy management systems(i.e., Automated Lighting, AC, Fan, Appliances Control), etc.

On the other hand, these sensors can also decipher different movements, making them useful in some industries where a customer can communicate with the system by waving a hand or performing a similar action. For example, someone can wave to a sensor in a retail store to request assistance with making the right purchase decision. Alternatively, you could also build apps that perform a similar action using Java application development or iOS.

Even though their primary use is correlated with the security industry, as technology advances, the number of possible applications of these sensors will only grow.

Some of the widely used motion sensor types:

• Passive Infrared (PIR): It Detects body heat (infrared energy) and is the most commonly used sensor in IOT for home security.
• Ultrasonic: Sends out pulses of ultrasonic waves and measures the reflection of a moving object by tracking the speed of sound waves.
• Microwave: This type of sensor sends out radio wave pulses and measures the reflection of a moving object. It covers a larger area than infrared and ultrasonic sensors, but it is vulnerable to electrical interference and is more expensive.

12. Accelerometer Sensors

An accelerometer is a transducer that measures the physical or measurable acceleration experienced by an object due to inertial forces and converts the mechanical motion into an electrical output. It is defined as the rate of change of velocity concerning time.

When an object moves or changes its orientation, an accelerometer can detect this and pick up those acceleration forces. Such forces result in a mechanical deflection or capacitive alteration within the sensor, leading to an electrical signal. Then the signal is analyzed to determine the magnitude and orientation of acceleration.

These sensors are now present in millions of devices, such as smartphones. They detect vibrations, tilting, and acceleration in general. This is great for monitoring your driving fleet or using a smart pedometer.

In some instances, it is used as anti-theft protection, as the sensor can send an alert through the system if an object that should remain stationary is moved.

They are widely used in cellular and media devices, vibration measurement, automotive control and detection, free-fall detection, aircraft and aviation industries, movement detection, sports academy/athlete behavior monitoring, consumer electronics, industrial and construction sites, etc. For example, in a smart car project, a .NET development company built a cross-platform app using these sensor data to evaluate driver behavior.

Various kinds of accelerometers used in IoT projects:

• Hall-effect accelerometers: Hall-effect accelerometers use the Hall principle to measure acceleration; they measure the voltage variations caused by changes in a magnetic field around them.
• Capacitive accelerometers: Capacitive accelerometers sense output voltage depending on the distance between two planar surfaces. They are also less prone to noise and temperature variation.
• Piezoelectric accelerometers: Piezoelectric sensing principle works on the piezoelectric effect. Piezo-film-based accelerometers are best used to measure vibration, shock, and pressure.

13. Gyroscope Sensors

A sensor or device used to measure angular rate or velocity is known as a Gyro sensor. Angular velocity is simply defined as a measurement of the rotation speed around an axis. It is used primarily for navigation and angular and rotational velocity measurement in 3-axis directions. The most critical application is monitoring an object’s orientation.

A gyroscope sensor consists of either a vibrating structure, spinning mass, or micro-electromechanical systems (MEMS), which can sense changes in angular velocity. Rotational movement creates changes in the moving structure of the sensor that are turned into electrical signals via the Coriolis effect. These signals are then processed to calculate the rotation rate (how fast it is spinning) and orientation (what direction is facing up/down/left/right).

Their main applications are in-car navigation systems, game controllers, cellular & camera devices, consumer electronics, robotics control, drone and RC helicopter or UAV control, vehicle control/ADAS, and many more.

Various gyro sensors are selected by their working mechanism, output type, power, sensing range, and environmental conditions.

• Rotary (classical) gyroscopes
• Vibrating Structure Gyroscope
• Optical Gyroscopes
• MEMS (micro-electro-mechanical systems) Gyroscopes

These sensors are always combined with accelerometers. The use of these two sensors provides more feedback to the system. With gyroscopic sensors installed, many devices can help athletes improve the efficiency of their movements as they gain access to the athlete’s movement during sports activities.

14. Humidity Sensors

A humidity sensor (or hygrometer) senses, measures, and reports both moisture content [Relative Humidity %] in the air or other gasses and temperature. It converts the humidity levels into an electrical signal to be readable.

Most humidity sensors use either capacitive, resistive, or thermal conductivity methods to measure the level of relative/absolute humidity. In a capacitive humidity sensor, changes in humidity alter the capacitance of a polymer or metal oxide layer between conductive plates. The resistive humidity sensors change the resistance along with the material. The moisture content in the air or gas affects its own thermal conductivity, which is used to sense humidity levels by measuring these changes. The sensor changes these to an electric signal, and by processing this, the humidity level is determined.

These sensors usually use temperature sensors, as many manufacturing processes require perfect working conditions. By measuring humidity, you can ensure that the whole process runs smoothly. When there is any sudden change, action can be taken immediately, as sensors detect the change almost instantaneously.

Their applications and use can be found in the industrial and residential domain for heating, ventilating, and air conditioning systems control. They can also be found in automotive, museums, industrial spaces and greenhouses, meteorology stations, paint and coatings industries, hospitals, and pharma industries to protect medicines.

15. Optical Sensors

An optical sensor is an IoT sensor type that measures the physical quantity of light rays and converts it into an electrical signal easily readable by the user or an electronic instrument/device.

An optical sensor uses a light source and a photoelectric receiver to determine the response of an app or device. The sensor measures the amount of light reaching the detector, based on whether no signal is present or changes in their signals. The light reflected by these objects is then collected as data and converted into an electric signal that is processed to calculate information like distance, presence, color, or any other physical property of the object.

IoT experts love optical sensors, as they are practical for measuring different things simultaneously. The technology behind this sensor allows it to monitor electromagnetic energy, which includes electricity, light, and so on.

Due to this fact, these sensors have found use in healthcare, environment monitoring, energy, aerospace, and many more industries. With their presence, oil, pharmaceutical, and mining companies are in a much better position to track environmental changes while keeping their employees safe.

Due to their electrical isolation, they are primarily used in ambient light detection, digital optical switches, and optical fiber communications. They are also best suited for oil and gas applications, civil and transportation fields, high-speed network systems, elevator door control, assembly line part counters, and safety systems.

Key types of optical sensors:

• Photodetector: It uses light-sensitive semiconductor materials like photocells, photodiodes, or phototransistors to work as a photodetector
• Fiber Optics: Fiber optics carry no current, So it’s immune to electrical & electromagnetics interference, and even in damaged conditions, no sparking or shock hazard happens.
• Pyrometer: It estimates an object’s temperature by sensing the color of the light. Objects radiate light according to their temperature and produce the same colors at the same temperature.
• Proximity & Infrared: Proximity uses light to sense objects nearby, and Infrared is used where visible light would be inconvenient.