Sensors are the backbone — or, more accurately, the central nervous system — of today’s technology. They unlock an essential level of connectivity that enables smart devices, the Internet of Things and intelligent automation to seamlessly run. These ubiquitous devices act as a machine’s eyes and ears, relaying information in real time and responding accordingly.
What Is a Sensor?
A sensor is a device that detects physical phenomena and converts it into electrical signals, producing a digital output. Depending on the type of sensor, it can capture and analyze a variety of external stimuli — heat, light, sound, pressure, magnetism or motion — and transmit measurements through a readable display.
18 Types of Sensors
There are a countless number of sensors — each with their own specific use case — and no set way to categorize them. Below is a list of some of the most common sensor types, detailing their unique qualities and everyday applications.
Temperature Sensor
A temperature sensor measures heat and cold of an object or space. It’s built into common items like thermometers and household appliances like water heaters, refrigerators and microwaves. Temperature sensors are a staple in climate control and industrial monitoring.
Pressure Sensor
A pressure sensor detects the force exerted by a fluid — liquid or gas — on a surface. This type of sensor is used for predictive maintenance to take care of industrial equipment, as well as monitoring automotive tire pressure in cars and patients’ blood pressure in medical care.
Position Sensor
A position sensor detects an object’s position and movement. It comes in many forms — including linear, rotary, proximity, tilt and incremental — and is commonly used in robotics, automotive systems and industrial machinery for accurate control and operation when tracking the position, orientation or displacement of components.
Proximity Sensor
A proximity sensor detects the nearness of an object without physical contact. Unlike a motion and position sensor, it’s not concerned with detecting movement. It works by emitting a continuous stream of signals — such as infrared light, ultrasonic waves or electromagnetic fields — and measuring how those return signals fluctuate to determine the distance of an object as it approaches. When a smartphone emerges from sleep mode as a user nears or auto-darkens the screen while on a call, that’s a proximity sensor in action.
Level Sensor
A level sensor measures the level of liquids, solids or granular materials within a container or system. It either reports when contents have passed a certain marker, known as point-level measurement, or continuously gauges the material’s rise and fall. A car’s gas tank, for example, features a level sensor.
Humidity Sensor
A humidity sensor measures the moisture content in the air. It powers instruments like hygrostats, hygrometers and humistors, which are commonly featured in HVAC systems, weather monitoring and industrial processes to relay humidity readings and prevent issues related to excessive moisture or dryness.
Flow Sensor
A flow sensor detects the rate at which a fluid, whether liquid or gas, moves through a system. This device uses acoustic waves and electromagnetic fields to measure the flow by tracking physical quantities like acceleration, frequency, pressure and volume. Water treatment, HVAC, and automotive systems use flow sensors to monitor and regulate fluid flow for efficient operation and safety, with particular importance in power plants and chemical industries.
Light Sensor
A light sensor, also known as a photodetector, measures light intensity. It works by converting photons into electrical energy, allowing a way to detect the intensity, wavelength, frequency or direction of light, depending on the purpose of an instrument. Everything from adjusting the brightness of a smartphone’s display screen to the aperture of a camera relies on light sensors. Surveillance and adaptive lighting systems, like those built into car headlights and streetlights, also use light sensors.
Color Sensor
A color sensor identifies the color of an object by analyzing the light reflected from it. Using red, green and blue filters, this device can measure the intensity of these values within a color, allowing it to determine the object’s overall chromaticity. Color sensors can provide information for color grading, sorting, quality control and automated systems.
Chemical Sensor
A chemical sensor detects specific chemical substances in the environment. To do this, it uses a receptor and a transducer to analyze changes in gas, odorant, ion and biological substances. Chemical sensors can detect contaminants in pollution monitoring, presence of explosives at airport security or the amount of chlorine in a pool.
Force Sensor
A force sensor measures the amount of applied force on an object. It tracks different types of mechanical forces — including weight, tension, compression, torque, strain, stress or pressure — and is commonly used in robotics and quality control across automotive testing and industrial machinery.
Motion Sensor
A motion sensor detects movement within a specific area. To do this, it monitors for changes in heat, infrared radiation or sound patterns using different tools, such as infrared, ultrasonic or microwave technologies. For example, accelerometers detect the rate of change in velocity of an object, while a gyroscope could detect its angular velocity. Intruder alarms, automatic sliding doors and touch-free hand dryers all employ motion sensors.
Sound Sensor
A sound sensor detects sound waves, then converts the acoustic signals to electrical ones for processing. Microphones, voice-command systems and security alarms use sound sensors that are designed to sense noise levels or identify specific sounds.
Contact Sensor
A contact sensor detects physical contact or pressure between two surfaces, and is triggered when that contact is broken. This security device is composed of two parts, a magnet and a sensor, and is typically installed to doors, windows or gates to alert homeowners of intruders.
Non-Contact Sensor
A non-contact sensor monitors an object without requiring physical contact. It uses wear-free technologies such as infrared, ultrasonic or capacitive sensing, and is widely used to operate automatic doors, X-rays and parking assistance systems that enable detection at a distance.
Infrared Sensor
An infrared sensor detects infrared radiation emitted by objects. This means it can sense an object’s presence or movement by heat fluctuations within range. Infrared sensors are commonly built into motion detection systems, thermal imaging and remote control devices.
Ultrasonic Sensor
An ultrasonic sensor measures the time it takes sound waves to reflect from an object in order to detect its presence, distance or movement. By pulsing a continuous stream of ultrasonic sound waves — those beyond human-hearing frequencies — the sensor can then calculate the distance based on the speed at which the sound waves travel back. It’s used to check fluid levels in tanks, car-parking assistance systems and take pictures of organs, tissues and babies in-utero to guide treatments and track growth.
Magnetic Sensor
A magnetic sensor measures the strength, direction and presence of a magnetic field. This device is of the non-contact variety, and is commonly featured in compasses, position tracking and industrial automation. Some common magnetic sensors include Hall sensors, which detect the magnetic flux density and outputs of a voltage, and magnetoresistance sensors, which detect shifts in an object’s resistance caused by a magnetic field.
Frequently Asked Questions
How many different sensors are there?
There is no set number of sensor types. But according to Grace Technologies, the five most commonly used sensors in control systems include temperature sensors, pressure sensors, level sensors, flow sensors and proximity sensors.
What is an example of a sensor?
Everything from a room’s thermostat (temperature sensor) to your car’s gas gauge (level sensor) operate with the help of sensors. Other examples include automatic doors (motion sensor), ultrasound machines (ultrasonic sensor) and smartphone touchscreen (non-contact, capacitive sensor).
