What is an Ultrasonic Sensor? Working Principle, Types, and Industrial Applications.
In industrial automation, some applications for measuring object presence or distance encounter conditions that classic photocells and capacitive sensors cannot handle. Transparent glass and plastic objects, bright and reflective surfaces, dust, fog, and even dark environments are among these challenging conditions. This is where ultrasonic sensor devices come into play. They emit high-frequency sound waves, imperceptible to the human ear, and measure the reflection to produce information about distance or object presence. Their ability to function regardless of color, surface characteristics, and lighting conditions has given them a unique position in the automation world.
Ultrasonic sensor devices generally operate at frequencies between 30 kHz and 500 kHz; lower-frequency models provide a wide coverage area, while higher-frequency models provide more precise measurements at a narrower angle. Models used in air environments are used for tasks such as storage tank level measurement, package size inspection, machine safety, and robot collision avoidance. Special models designed for liquid environments excel in flow rate measurement and level monitoring applications.
Ultrasonic Sensor Working Principle
Ultrasonic sensor devices operate on the principle of knowing the speed of sound waves in air and measuring the time it takes for the wave to travel and return. Sound waves travel at approximately 343 m/s in air; this value varies with temperature. The sensor sends a sound wave by vibrating a piezoelectric crystal at a high frequency. This wave hits an object in front of it, reflects back, and is detected by the same crystal. The distance is calculated by measuring the time between transmission and detection.
A typical device first produces a short vibration signal during measurement; then the crystal switches to receiver mode and waits for the returning echo. During this time, external vibrations and electromagnetic interference are filtered out; only reflections with the expected frequency and characteristics are evaluated. Modern models include a temperature compensation circuit; this ensures that changes in ambient temperature do not affect measurement accuracy. Some models can analyze multiple reflections to provide the closest object, the average distance, or the furthest reflection.
Ultrasonic Sensor Structure
The device’s internal structure consists of a piezoelectric transducer, driver circuit, receiver amplifier, temperature sensor, processor, and output stage. The piezoelectric transducer is used both to transmit sound waves and to detect the reflected wave. The driver circuit applies a high-frequency signal to the transducer, putting it into ringing mode. The receiver amplifier amplifies the returning weak signal, bringing it to a level that the processor can utilize.
The main structural components of the device are briefly as follows:
- Piezoelectric transducer (transmitter and receiver)
- High-frequency driver circuit
- Low-noise receiver amplifier
- Internal temperature compensation sensor
- DSP/ARM-based processing unit
- NPN, PNP, analog (4-20 mA, 0-10 V) output stage
- IO-Link, Modbus, Profinet communication interface
- Stainless steel or PVDF coated housing
- IP65 / IP67 / IP69K level sealing
Applications of Ultrasonic Sensors
Ultrasonic sensor devices are used in many applications where classic photocell and capacitive sensors are insufficient. Transparent glass bottles, plastic containers, and shiny metallic surfaces are reliably detected by these sensors; this feature is a major advantage in beverage production, pharmaceutical packaging, and glass manufacturing. Object presence, package size, and height measurement on moving conveyor lines are also performed using these sensors.
Applications where this technology is heavily utilized include:
- Liquid, granule, and powder level measurement in tanks and silos
- Presence of transparent glass bottles in beverage production
- Roll diameter measurement in paper and cardboard machines
- Collision avoidance in robotic and AGV vehicles
- Vehicle detection in parking and traffic counting systems
- Human detection in automatic door systems
- Clamp-on types for water flow measurement
- Presence detection in washable hygienic food environments
Advantages of Ultrasonic Sensors
The greatest advantage of these devices is their ability to detect objects regardless of material type. Almost all solid and liquid surfaces can be detected by these devices, regardless of whether they are transparent, glossy, matte, colored, dark, shiny, or absorbent. This feature is a decisive advantage in dealing with transparent glass and plastic objects, which classic photocell sensors cannot handle. They can operate reliably even under adverse visibility conditions such as dust, fog, steam, and darkness.
Thanks to their wide operating temperature ranges, stainless steel housing models, and high protection classes, they operate reliably in harsh industrial environments. Their ability to transmit distance measurements directly in analog or digital form enables complex applications such as object size verification on production lines. Thanks to temperature compensation circuits, they are minimally affected by changes in ambient temperature. Modern models transmit not only distance but also signal amplitude, temperature, and diagnostic information to the PLC via IO-Link communication.
Ultrasonic Sensor Selection
To select the correct ultrasonic sensor, the measurement range must first be determined. Compact models are recommended for close-range applications (5 cm-50 cm), standard cylindrical models for medium range (50 cm-3 m), and high-power models for long range (3 m-10 m). The blind spot distance (the area in front of the sensor that it cannot detect) varies from model to model, and measurements outside this area should be targeted in the application. Resolution requirements are evaluated together with the measurement repeatability rate.
The surface characteristics of the target object are important. Flat and wide surfaces efficiently reflect sound waves back to the sensor; reflection is weaker on inclined or rough surfaces. High-power models are recommended for soft and absorbent surfaces. Environmental conditions such as temperature, humidity, dust, airflow, and vibration should be considered. Temperature-compensated models are recommended for models that will operate outdoors. ATEX-certified models should be selected for explosive environments. PVDF-coated stainless steel models are preferred for corrosive chemical liquids; IP69K rated stainless steel models are preferred for washable, hygienic food areas.
Ultrasonic Sensor Supply via Elektraverse
Elektraverse is an AI-powered B2B digital marketplace developed specifically for the electrical and electronics industry, matching buyers and suppliers based on technical compatibility for your ultrasonic sensor purchases. Unlike traditional price-focused marketplaces, its approach prioritizes engineering requirements such as measurement range, blind spot distance, accuracy, housing material, protection class, operating temperature, ATEX certification, output type, and communication protocol. When you enter your project’s technical requirements into the request form, the AI algorithm automatically directs your request to the most suitable models among the registered suppliers.
Thanks to its direct communication structure that eliminates intermediaries, the technical question-and-answer process is shortened, and the quotation collection time is significantly reduced. Elektraverse also creates a vast technical knowledge base on ultrasonic applications, tank level measurement, IO-Link technology, and hygienic production sensors through blog posts, webinar recordings, and YouTube content. You can directly submit your technical questions before sensor selection using the Elektraverse Assistant chat application within the site.
Frequently Asked Questions
What objects can ultrasonic sensors detect?
These devices detect all surfaces that reflect sound waves, regardless of material type. This includes metal, plastic, wood, glass, liquids, powders, granules, paper, and human tissue. Color, brightness, or transparency do not affect the measurement.
What is the difference between ultrasonic and laser rangefinders?
Laser rangefinders provide very high accuracy (micron level); however, problems may occur with transparent or very glossy surfaces. Ultrasonic types detect transparent and colored surfaces without problems, but their accuracy remains at the millimeter level and can be affected by air currents.
What does sensor blind spot mean?
The blind spot is the closest area in front of the sensor where it cannot detect anything. Models typically have a blind spot ranging from 4 to 30 cm; in practice, the target object must be placed outside this area.
Are these sensors affected by air temperature?
The speed at which sound waves propagate through air varies with temperature. Modern models have an integrated temperature compensation circuit that eliminates this deviation. The accuracy of certified models is kept stable between -20 °C and +60 °C.
What data does IO-Link provide?
The IO-Link interface transmits distance data from these devices, as well as receiver signal amplitude, ambient temperature, switching count, and diagnostic alerts. This is a useful feature for predictive maintenance.