How Do Ultrasonic Sensors Work?
Ultrasonics refers to signals that are above the human hearing span (>20 kHz). There are several types of Ultrasonic transducers. Industrial Ultrasonic sensors that measure through air generally transmit between 30 KHz and 500 KHz. As the ultrasonic frequency increases, the rate of attenuation increases. Thus, low-frequency sensors (30–80 kHz) are more effective for long range, while high-frequency sensors are more effective for short range. Higher frequency sensors (80–500 kHz) also reduce the ringing-decay, which allows for a shorter minimum detection range.
Most ultrasonic sensors for testing purposes, such as for non-destructive (NDT) testing, transmit at higher frequencies and generally between 1 MHz and 10 MHz. Ultrasonic sensors for medical ultrasound applications are also higher and transmit generally in the 1 MHz – 20 MHz range for imaging purposes, and below 2 MHz for therapeutic purposes.
Industrial ultrasonic sensors that transmit through air in the range of 30 KHz to 300 KHz are used wherever non-contact distance measurement is desirable. These types of ultrasonic sensors (sometimes called ultrasonic transducers) measure the distance to or the presence of a target object by sending a sound pulse, above the range of human hearing (ultrasonic), toward the target and then measuring the time it takes the sound echo to return. Knowing the speed of sound, the sensor determines the distance of the target and sets its outputs accordingly. If temperature changes or fluctuations are present, some ultrasonic sensors can automatically apply an offset scaling for temperature compensation. Applications fall into three general categories:
- Tank Level – liquids & solids in open and closed tanks
- Water Monitoring – Managing for conservation, efficiency, and safety
- Water Management – Water level in streams, canals, channels, and ponds
- Liquid Flow – Measuring liquid height in flumes, weirs, and channels to calculate volumetric flow of water and eluents
- Flood & Tsunami Warnings – Level of streams and bodies of water to warn communities
- Fuel Monitoring – For inventory of fuel, usage, theft
Distance Ranging & Dimensional
- Roll Diameter – Paper, film or foil to identify web tension, amount on a roll
- Loop Control – measuring the free loop of material as it is being moved from one machine to another to prevent breakage
- Height & Size – Objects such as boxes, containers, etc.
- Position feedback – The position of an object can be used in a closed loop system to maintain or control position
Object Detection or Proximity Detection
- Objects can be detected for security, counting, inventory or robotic obstacle avoidance. People can be detected at kiosks or determined to be approaching or leaving. Targets can be monitored over the full sensor range or restricted within user-defined distance ranges
- For longer range applications for detection, presence, or absence of objects or materials, obstacle avoidance, etc.
Industrial ultrasonic sensors will detect both large and small targets, including liquids, solids and granular materials. The size, shape and orientation of the target will affect the maximum distance at which it can be detected, and the sensor is not affected by optical characteristics such as color, reflectivity, transparency, or opaqueness.
How Are Ultrasonic Sensors Used?
Need to know how much diesel fuel is in the tank, how high the water level is under the bridge, or whether the chicken feed will last longer than the chickens? Do you want to ensure the proper amount of water is fed to crops, monitor for theft or a spill from a tank? Is turning on a pump to refill a tank, or start a motor when the level gets to a certain point, or trigger an alarm? Ultrasonic sensors are used in these and hundreds of more applications.
Ultrasonic sensors will detect both large and small targets, including liquids, solids and granular materials. They are used with electrically noisy machinery including motor drives and other electrical and electromechanical controls. Non-contact ultrasonic sensors have distinct advantages in challenging environments where corrosive, scaling, coating, or dirty materials are likely to negatively impact the performance and maintenance costs of contact sensors. Non-contact ultrasonic sensors are also desirable where the material being measured cannot be corrupted by contact with any measuring device.
Temperature can affect an industrial ultrasonic sensor but can be compensated for with the right sensor. Humidity change is generally not a significant factor (0.036% / 10% RH change). Normal atmospheric pressure changes or small pressure changes in vessels will not affect ultrasonic sensor operation either.
High-Quality Ultrasonic Sensors From Senix
Ultrasonic signals give autonomous and no-contact tools the ability to register nearby obstacles and surfaces. At Senix, we manufacture an array of ultrasonic sensors for use across different industries and applications. Contact us today to see how our distance and level sensors can benefit your operation, or browse our online catalog now. For assistance with selecting the right ultrasonic sensor for your needs, check out our selection guide.
Ultrasonic Sensor Selection Guide
Ultrasonic sensors are engineered to measure the distance to a remote object through the air without physically touching it. They determine this value by emitting high-frequency (ultrasonic) soundwaves toward the object being measured, receiving the reflected wave, and calculating the time between emission and reception. Due to their unique operational characteristics, these distance measurement sensors find use in a wide range of industrial and scientific applications where non-intrusiveness is critical. As a result, ultrasonic sensor manufacturers produce sensor products in numerous variations to meet different measurement requirements and restrictions. While this broad selection makes it possible for customers to find a sensor that suits their unique application, it can also make it more difficult to determine which one is right. Fortunately, the experts at Senix are here to help.
At Senix, we specialize in designing, manufacturing, distributing, and supporting high-quality ultrasonic sensors. Equipped with over 30 years of experience supplying these non-contact distance measurement sensors to end-users and original equipment manufacturers (OEMs) across a variety of industries, we have the expertise to help customers identify the right product for their needs.
In the following guide, we detail the ultrasonic sensor selection criteria we consider when providing customers with product selection assistance. Choosing the ideal sensor depends on numerous variables, including:
- The measurement application
- The distance of the object being measured
- The output requirements
- The environmental conditions
What Is the Measurement Application?
Ultrasonic sensors are used in various non-contact distance measurement applications, each of which carries different requirements and restrictions. The sensor you choose should fulfill the demands of your application, whether you need stainless steel sensors for corrosive environment operations, cross-talk-resistant sensors for multi-sensor operations, or wireless-enabled sensors for remote measurement operations.
Typical applications for Senix ultrasonic sensors include:
- Water Monitoring: They measure the level of water to facilitate irrigation, stream, river, canal and sea monitoring, and floor and tsunami warning operations.
- Tank Level Monitoring: They measure the level of materials within a tank to calculate the current volume and indicate if and when the tank must be refilled.
- Distance Ranging: They measure the distance to an object for dimensioning, positioning, and object ranging operations.
- Object Detection: They detect whether an object is present, rather than the distance between them and the object, within a specific distance window.
- Hydrofoil & Nautical: They calculate the flying height of hydrofoil and other types of boats.
- Wireless Level Monitoring: They measure material levels within streams, tanks, and other targeted areas and wirelessly transmit the information to authorized users for remote monitoring.
In all of these applications, it is important to consider the chemical characteristics of the object being measured when choosing the sensor design and construction. For example, if water is being measured, a general-purpose sensor may suffice. On the other hand, if a strong chemical is being measured, a more chemical-resistant model (e.g., ToughSonic CHEM) may be more appropriate.
What Is the Maximum/Minimum Measurement Distance?
If a sensor is too close to an object, it may not be able to measure the distance accurately. If a sensor is too far from an object, it may not detect the object at all. The sensor chosen for a distance measurement application must be properly rated for the expected minimum and maximum measurement distances. Factors to consider when determining the useful operating range required (i.e., the material window) include:
- Material State: Liquids and solids behave differently when hit with soundwaves, which results in different interactions with ultrasonic sensors. For liquid measurement applications, we recommend choosing a sensor with a range that is at least 25% greater than the expected maximum measurement distance. For dry measurement applications, we recommend a sensor with a range that is at least 50% greater than the expected maximum measurement distance.
- Size, shape, and orientation. The size, shape, and orientation of the material affect the maximum distance at which it can be detected. Large, flat water surfaces are among the easiest to detect at a distance, while curved or granular objects are harder to detect at a sensor’s maximum range.
Senix sensors are available with a maximum measurement distance of about 50 feet. Different models offer different maximum measurement distance ranges—e.g., general-purpose (50 feet), chemical (35 feet), and hazardous area (25 feet).
What Sensor Output Is Preferred?
Sensor outputs are set based on the measurement reading or, in override conditions, the lack of a detected target or user-selected response algorithms. Senix ultrasonic sensors can provide one or more simultaneous outputs to various connected devices (e.g., computers, displays, programmable logical controllers, etc.). The output options available are:
- Analog: the voltage or current output signals vary proportionally to the measured distance
- Switch/Relay: the switch outputs turn on or off at set distances to start and stop certain external actions or indicators at predetermined distances
- Serial Data: the output data is transmitted sequentially to a connected device
When choosing between these three output options, it is important to consider the type of system you are plugging the sensor into and the devices connected to the sensor.
What Are the Application Environment Conditions?
Ultrasonic sensors can offer reliable distance measurement performance in a variety of industrial environments. However, they must be engineered to withstand the conditions found in that environment. Some of the environmental factors to consider when choosing an ultrasonic sensor include:
- Temperature: The speed of sound varies depending on temperature, which can affect the accuracy of the distance measured between the sensor and the targeted object.
- Weather: Ice, snow, dust, mud, and other environmental material buildup can block the sensor face, which can prevent the ultrasonic soundwaves from being transmitted or received. Additionally, the ingress of contaminants, such as water, can affect sensor function. ToughSonic sensor models are constructed with full epoxy potting, UV-shielded cables, and IP68 / NEMA-4X / NEMA-6P stainless steel or polymer housings to ensure durability in harsh outdoor environments.
- Pressure/Vacuum: Ultrasonic sensors are not designed for use in high-pressure or vacuum applications.
- Ultrasonic noise: Ultrasonic noise generated by nearby equipment (e.g., air nozzles, pneumatic valves, and ultrasonic welders) can interfere with measurement operations. Computable programmable models can be configured to ignore these effects.
Senix: Your Expert and Partner for Ultrasonic Sensor Need
Ultrasonic sensors play an essential role in a wide range of non-contact distance measurement applications. For sensors you can rely on in your most critical operations, turn to the experts at Senix.
Our sensors find use in demanding distance measurement applications across the globe. Check out our ultrasonic sensor selection! For additional information about our products or assistance choosing one for your needs, contact us today.