What Is an Ultrasonic Sensor?
An Ultrasonic Sensor can measure distances by sending out high electrode frequency sound vibrations or high frequency waves (usually between 20 kHz and 200 kHz) and waiting for the echoes. Ultrasonic Sensors can perform the measurement with the travel-time of an echo from the object and determines the distance to that object. The sensor is able to detect objects, measure distances and track movement in conditions where light-based sensors are not suitable.
Unlike optical sensors which are based on the principle and propagation of light, ultrasonic sensors are based on the principle of sound. This allows them to work in an environment that is dusty, smoky or in poor light. They are also able to detect transparent or shiny surfaces like glass, metal or liquid accurately and consistently. They are widely used in industrial automation, automotive electronics and medical instruments.
Key advantage: Ultrasonic sensors measure distance without touching, which is especially useful for applications involving fragile, hot or dangerous materials
Ultrasonic sensors play an important role across multiple industries, including automotive electronics, industrial control and medical technology.
Main Types of Ultrasonic Sensors
Ultrasonic sensing technology divides into four main product categories based on the measurement task. Selecting the right type is the first decision in any sensor specification process.
Ultrasonic distance sensors take care of positioning and obstacle detection as well as measurement of proximity for robotics and automotive systems.
Ultrasonic level sensors oversee fill levels uninterruptedly in tanks, silos and open channels without having to come in contact with the process medium.
Ultrasonic flow sensors determine the fluid velocity in pipes without error, have no moving parts and suffer no pressure drop where they are read.
Reliable ultrasonic proximity sensors detect the presence of objects on materials and geometries that defeat the use of optical methods.
How an Ultrasonic Sensor Works
An Ultrasonic Sensor can measure distances by sending out high electrode frequency sound vibrations or high frequency waves (usually between 20 kHz and 200 kHz) and waiting for the echoes. Ultrasonic Sensors can perform the measurement with the travel-time of an echo from the object and determines the distance to that object. The sensor is able to detect objects, measure distances and track movement in conditions where light-based sensors are not suitable.
Pulse Transmission
The piezoelectric transducer converts an electrical signal into a short burst of ultrasonic waves — typically at 25 kHz to 400 kHz. Higher frequencies give better resolution; lower frequencies provide greater measurement range.
Echo Reception
The sound wave travels through the medium, reflects off the target surface, and returns to the transducer (or a separate receiver). The same piezoelectric element often functions as both transmitter and receiver in alternation.
Signal Processing & Output
The microcontroller measures the time between pulse transmission and echo reception. Distance = (time × speed of sound) ÷ 2. The result is output as analog voltage, current (4–20 mA), or digital signal (IO-Link / PWM / UART).
The speed of sound in air varies with temperature — approximately 0.6 m/s per °C. Most industrial-grade sensors include integrated temperature compensation to maintain accuracy across operating conditions.
Core Specifications That Matter
Eight parameters define the performance envelope of any ultrasonic sensor. Understanding each one lets you match the component to your application — rather than over-specifying or discovering limitations after installation.
| Parameter | Typical Range | Why It Matters |
|---|---|---|
| Measuring Range | 2 cm – 10 m+ | Defines the min and max distance the sensor can reliably detect. Must account for target size and surface material. |
| Blind Zone | 2 cm – 30 cm | Dead zone in front of the sensor where detection is unreliable. Your minimum detection distance must exceed this value. |
| Accuracy | ±1 mm – ±1% | How close the measured value is to the true distance. Key for positioning, fill-level control, and precision automation. |
| Operating Frequency | 25 kHz – 400 kHz | Higher = better resolution, narrower beam, shorter range. Lower = longer range, broader beam, lower resolution. |
| Beam Angle | 5° – 30° | Defines the detection cone. Narrow beams give precise targeting; wide beams cover larger areas but may detect unwanted objects. |
| Response Time | 10 ms – 100 ms | How quickly the sensor outputs a new reading. Critical for high-speed conveyor lines and fast-moving robot systems. |
| Output Type | Analog / Digital / IO-Link | Determines interface compatibility with PLC, MCU, or fieldbus. IO-Link enables remote parameter setting and diagnostics. |
| IP Rating | IP65 – IP68 | Protection against dust and water ingress. IP67/IP68 required for washdown environments and outdoor installations. |
Need a specification checklist for your application? Our engineers can help match the right parameters to your environment and performance requirements.
Where Ultrasonic Sensors Are Used
Every application environment places different demands on range, accuracy, environmental protection, and output interface. Understanding your scenario is the first step to the right specification.
Industrial Automation
Object detection, part counting, position verification, and gap measurement on production lines. High-speed response and narrow beam angles are critical.
Automotive Systems
Parking assistance, blind-spot detection, and AV proximity sensing. Wide temperature range and EMC compliance required.
Liquid Level Monitoring
Non-contact level measurement in tanks and chemical vessels. IP67/68 and chemical-resistant housings essential for aggressive media.
Pipeline Flow Measurement
Transit-time and Doppler flow sensors for water, oil, and gas. Clamp-on variants allow installation without pipe modification.
Robotics & AGV
Collision avoidance, navigation assistance, and proximity detection for autonomous guided vehicles near human workers.
Smart Agriculture
Crop canopy height, soil moisture detection, and silo fill-level monitoring. Rugged outdoor ratings and wide temperature tolerance required.
Ultrasonic vs Infrared Sensor
This blog is designed to develop your intuition beginning from the underlying physical principles up to practical physical and engineering decisions in order to make the correct sensor decision for every application.
| Ultrasonic Sensor | Infrared Sensor | |
|---|---|---|
| Material Sensitivity | No impact | Dark surfaces absorb IR |
| Range of Detection / Coverage Pattern | Long range | Short distance |
| Environmental Interference Resistance | Not affected | Strong sunlight causes interference |
| Measurement Precision and Response Speed | A typical measurement cycle takes 20-50 milliseconds,+/- 1mm of controlled accuracy | Under 1 millisecond,measurement frequencies over 1kHz |
| Dead Zones | Ultrasonic sensors normally can not sense the objects which are close to it less than 2-3cm | Infrared triangulation sensors have geometric limitations. |
How to Select the Right Ultrasonic Sensor
Follow this five-step process to move from application requirements to a fully specified sensor that fits your environment, interface, and performance needs.
Define Measurement Type
Distance, level, flow, or presence detection? Each requires a different sensor architecture and output format. Getting this right eliminates most wrong choices immediately.
Set Range & Blind Zone Requirements
Define minimum and maximum detection distances. Your minimum required detection distance must be greater than the sensor's specified blind zone — otherwise the target will be invisible.
Confirm Accuracy Requirement
Position control typically needs ±1 mm. Level monitoring may accept ±5 mm. Match the sensor specification to your process tolerance — over-specifying adds cost with no benefit.
Check Environmental Conditions
Temperature range, IP rating, chemical exposure, and EMC requirements. Any outdoor or washdown application requires IP67 minimum. Temperature ranges beyond −10°C to +70°C require industrial-grade selection.
Choose Output Interface
Analog (0–10V / 4–20 mA), digital switching (NPN/PNP), or IO-Link? Match to your PLC or controller's available inputs. IO-Link is the preferred choice for new automation projects where the controller supports it.
Not sure which configuration fits your application? BESTAR's engineers review your system requirements and recommend the right sensor within 24 hours.
Deep-Dive Articles
Each article below covers a specific technical or commercial aspect of ultrasonic sensors in full depth. Start with whichever topic is most relevant to your current project stage.
BESTAR Ultrasonic Sensor Series
BESTAR's portfolio is organized around measurement type and application priority. Each series targets a distinct performance requirement — not just a model number.
Distance & Proximity
Compact sensors for object detection, positioning, and collision avoidance in industrial automation and robotics.
View Series →Liquid Level
Non-contact level sensors for tanks and open channels. IP67/IP68 with chemical-resistant housings.
View Series →Flow Measurement
Clamp-on and inline flow sensors for liquid pipelines. Non-invasive installation, no process shutdown.
View Series →OEM Custom
Custom frequency, output interface, housing, and cable assembly. Full OEM/ODM support from spec to production.
Request →Frequently Asked Questions
The blind zone is the smallest distance that can be detected (from the point closest to the sensor face to the sensor face) and the sensor can read. In this zone, the transducer is still "transmitting" after sending out a sound pulse, and is not yet “listening” for an echo.
No. They are a type of the ultrasonic sensors, and are designed to operate in air. They transmit a wave of sound in air and receive an echo from a surface. Liquid materials and solids both have separate acoustic parameters - most of the signal is not transmitted through the material.
A distance is measured at ultrasound by making use of a sound pulse. The speed of sound depends on temperature and this depends on cylinders located in the building, the temperature of the surrounding gas and the distance between the wall and the cylinders. A 50°F(10 °C) error would cause a measurement drift of approximately 0.07in(1.7mm) when the distance to the test object is 39.37in(1 m).
Analog (4-20 mA / 0-10 V): Provides a continuous signal in proportion to distance. Easy, universal and right connected with any PLC analog input. Should you require a single distance value and already have analog infrastructure in your system, you should go with best choice.
It is harder to have foam. The ultrasonic pulse is absorbed and scattered by foam instead of being reflected totally. The thickness of the foam layers will cause the sensor to measure the reflective surface when it is used to detect the liquid underneath, or not detect it at all. These sensor will work quite well for foam-heavy applications, where greater sensor output power and stronger echo filtering are required. A stand pipe or measurement tube is also a practical solution.
Yes. Common customizations include: