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 ApplicationsLiquid Level 

  • Tank Levelliquids & solids in open and closed tanks
  • Water MonitoringManaging 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.