Frequently Asked Questions

Ultrasonic sensors, sometimes called ultrasonic transducers, measure the distance to or the presence of a target object. An ultrasonic sound pulse that is above the range of human hearing is sent toward the target, then the time it takes the sound echo to return is measured. Knowing the speed of sound, the sensor determines the distance of the target and sets its outputs accordingly. Learn more about our technology…

Sensor outputs are set based on the measured distance, a lack of target detection, override conditions, or user-selected response algorithms. Outputs can be:

• An analog voltage or current signal proportional to the measured distance
• Switches or relay contact closures that open or close at specific distance
• Distance data transmitted as serial data communications

Ultrasonic sensors measure the distance to—or presence of—a target object or material through air without touching it. The measured distance is provided as an output in a variety of standard electrical interfaces compatible with displays, machinery, programmable logic controllers (PLCs), computers, and most electronic or electrical machinery.

Non-contact ultrasonic sensors have distinct advantages in challenging environments where corrosive, scaling, coating, or dirty materials are likely to impact the performance and maintenance costs of contact sensors. Non-contact ultrasonics are also desirable if the material being measured needs to be kept sterile, sanitary, or out of contact with any sort of measuring device.

Seeking more product guidance before picking your ToughSonic®? Our selection guide is a great place to start.

Ultrasonic sensors are used wherever non-contact distance measurement is desirable. Senix sensors are currently operating reliably on thousands of machines and environments in many industries throughout the world. Technical and product assistance is readily available to all users.

Applications range from simple liquid level measurements to diameter measurements: converting machinery and robot positioning in automated warehouses. Senix can also configure, adapt, or design sensors for custom needs.

Applications fall into three general categories:

Liquid Level Measurement − Measuring the Height of Liquids

Industries monitor liquid levels in tanks, vats, drums, bins, lift stations, flumes, weirs, and stilling tubes. Environmental monitoring applications measure the ocean surface for tsunami warnings, river and stream levels for flood warnings, and irrigation channels and ponds for water delivery. Where there is liquid, there is usually a need for inventory or level control. Read more about Water Monitoring or Tank Level Monitoring applications...

Object Detection − Detecting the Presence of Objects or People

Objects often need to be detected for security, counting, inventory, or robotic obstacle avoidance. Ultrasonic sensors are not affected by the object’s color or optical characteristics such as reflectivity, transparency, or opacity. At kiosks, sensors can determine if people are approaching, lingering, or leaving. Targets can be monitored over the full sensor range or restricted within user-defined distance ranges. Learn more about Object Detection applications…

Distance Ranging and Dimensioning — Measuring Location

Senix sensors can discriminate objects by height or size, such as when selecting and routing boxes on a conveyor or rejecting out-of-dimension objects. Converting machines measure changing roll diameter to control web tension. Other applications measure the location of a target object for display or control feedback. Examples include dancer roll and web loops in printing and converting machinery, camera focusing, mirror positioning in flight simulators, robotic positioning, and much more. Learn more about Distance Ranging applications…

ToughSonic® sensors can 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. Sensors are not affected by optical characteristics such as color, reflectivity, transparency, or opaqueness.

These general sensor mounting guidelines should be adhered to. For more complex mounting guidance, please contact Senix Customer Service for product assistance.

• Ultrasonic sensors should be mounted in plastic threaded adaptors to avoid acoustic energy absorption through the sensor body
• Sensors should be hand tightened only—never apply a wrench to the sensor body
• When mounting to a domed or round tank, adjust the sensor mount until the transducer face is square with the target surface
• Mount the sensor directly to the tank ceiling at a flange opening. If a riser is added, it must be of sufficient diameter to cause no inner wall reflections. Round off the lower edge of the riser
• Provide a sunshade for outdoor installations to prevent the sensor body from overheating and causing erroneous measurements. The sensor body should remain equal to the ambient air temperature so the sensor’s built-in temperature compensation can function correctly

NO—DO NOT USE any ultrasonic sensor as a primary safety device to detect and protect people! Although ultrasonic sensors generally detect people reliably, an ultrasonic echo may not be detected if a person is at the wrong angle or is wearing ultrasonically absorbent clothing.

Ultrasonic sensors can be used as secondary devices for additional safety, but they should never be used in an application where life or health are at stake!

They DO NOT measure through tank walls—they only measure through air.

They DO NOT measure material thickness by contacting the material. Try non-destructive testing (NDT) sensors for that application.

They DO NOT work in a vacuum, as sound does not travel.

They DO NOT work at temperatures above 158°F (70°C) or high pressures.

They DO NOT locate objects moving about in a three-dimensional (3D) space.

They DO NOT measure farther than about 70 ft (21 m).

They DO NOT measure at very high repetition rates. Due to speed of sound limitations, the fastest rate is 200 Hz at a max distance of about 24 inches.

They DO NOT work as accurately in vaporous environments that change the speed of sound from that of air.

The maximum range of our products is presently about 50 feet (15.25 meters). This range varies by model. For product assistance, contact the Senix team today.

The distance at which an object is detected depends on its size, shape, and orientation. In general, the target must be larger to be detected from farther distances, since the object must reflect a sufficient ultrasonic echo back to the sensor to be detected. Large, flat targets—such as a liquid surface in a tank—are detected at the maximum range. Curved objects or sound-absorbing materials, like fabrics or non-wovens, reflect less energy directly back to the sensor. Granular materials may absorb or deflect sound energy away from the sensor due to surface variation and/or angle of repose. The sensor maximum range is derated for these targets.

Other factors affect how close an ultrasonic sensor can be to a target, yet still accurately measure distance.

• When too close, the sensor will not detect the first echo, but may detect a second or third echo, yielding a longer than actual value. This deadband distance varies by model and is larger for longer range models, varying from 1.75 to 14 inches (44 to 305 mm)
• The minimum range and maximum range define the limits of the material window, which is the useful operating range of the sensor. This window is user-adjustable with SensorView™ software to ignore unwanted targets or optimize system performance
• When used outdoors, we recommend limiting the range to the sensor’s “Optimum Range” specification rather than the “Maximum Range” to allow for environmental extremes

Most of Senix’s sensors are configurable with SensorView™ software. This is the ultimate tool for quick setup and superior visibility in any application.

SensorView provides a wide range of sensor configuration options and several displays of sensor measurements, allowing users to better optimize performance. Complete sensor installations can be saved for quick repair or duplication.

For technical assistance with SensorView, contact Senix’s team today.

Most ToughSonic® models have a measurement resolution of 0.003384 inches (0.086 mm).

Other measurement, environmental, and target factors affect the overall result. Typical repeatability is better than 0.5%, and accuracy is better than 1% of the measured target distance. Learn more about Ultrasonic Accuracy and Specifications here.

ToughSonic® sensors are housed in rugged materials and fully potted in epoxy resin. If you select the correct Senix sensor for your application, very little maintenance is required.

It’s important to keep the ultrasonic transducer face clear of ice, snow, dirt, and other physical barriers to prevent disruption of the ultrasonic signals. Ideally, sensors will be mounted with transducer faces pointed downward to minimize material collection on the face. If transducer faces do require cleaning, pressurized air can be used.

In liquid level applications, occasional submersion or spraying of the material being measured is often sufficient to maintain a clean transducer face. Sensors with exposed transducer faces can also be cleaned with alcohol or window cleaner, if necessary.

DO NOT use solvents such as butanone (MEK) or acetone on ToughSonic sensors with exposed transducers.

Our sensors operate reliably in even the most extreme industrial environments. They can be utilized alongside electrically noisy machinery, including motor drives and other electrical and electromechanical controls. Specific product selection considerations include:

Ingress Ratings

The ToughSonic® line is IP68 / NEMA-4X / NEMA-6P rated and will operate after complete submersion.

Outdoor Environments

ToughSonic models are designed to withstand the harshest outdoor environment with full epoxy potting, UV-shielded cables, and stainless steel or polymer housings. The sensor face must be protected from ice, snow, mud, or other buildup, or the transmission of sound energy will be reduced or blocked.

Temperature

The temperature of the air between the sensor and the target can affect measurement accuracy, since the speed of sound varies with temperature. If this is an issue, temperature compensation is available in all computer-configurable models.

At room temperature, the speed of sound changes approximately 0.175%/°C, or 1% for every 5.7°C. As the temperature increases, the target will measure closer, and vice versa.

Air temperature variations or gradients between the sensor face and the target will affect accuracy because the sensor assumes a constant temperature when it calculates distance. This can be an issue in vertical measurements, such as a tank level, if internal heating occurs when the tank is exposed to the sun, creating a temperature gradient inside the tank.

Some customers have had success with hot applications. Environments above 158°F (70°C) are not recommended. In general, readings become less reliable in a non-homogeneous environment.

Severe temperature gradients, such as measuring red-hot metal, cause the echo to reflect off the gradient rather than the intended target. This makes measurements invalid.

Humidity

Humidity change is generally not a significant factor (0.036%/10% RH change).

Pressure/Vacuum

Normal atmospheric pressure changes or small pressure changes in vessels will not affect ultrasonic sensor operation. However, ultrasonic sensors are not designed for high pressure applications, as sound does not travel in a vacuum.

Audible Noise

Loud audible noises produced by machinery do not affect the sensor.

Ultrasonic Noise

Locally generated ultrasonic noise at the sensor operating frequency can interfere with measurements. Some potential sources are high pressure air releases near the sensor caused by air nozzles, pneumatic valves or solenoids, or ultrasonic welders. In computer-programmable sensors, processing options can be selected to ignore the effects of noise bursts.

Higher-frequency sensors are less susceptible to noise interference since there is less high-frequency noise in the air due to sound absorption. Air paths are usually rearranged, blocked, or eliminated to prevent this.

Senix sensors are designed to enable several ultrasonic sensors to operate in the same vicinity without mutual interference.

ToughSonic® sensors provide measured distance information in several analog and serial data formats. Sensors can have one or more simultaneous outputs in various combinations for connection to displays, Programmable Logic Controllers (PLCs), computers, motor drives, and almost any type of electronic equipment. The following output types are available:

Analog Output

Voltage or current signals that vary proportionally with the measured distance. Some sensor models provide two or three simultaneous analog outputs.

Analog distance endpoints are easily set anywhere within the sensor’s measurement range. Either endpoint can be the analog high limit or analog low limit, allowing either a positive or negative slope.

Standard analog output value selections include 0-10 VDC, 0-5 VDC and a 4-20 mA current loop. Computer-configurable models permit user-entered analog high and low limit values.

Switch/Relay Output

Switch outputs turn ON or OFF at a distance setpoint. They are used to start and stop external actions or indicators at those distances.

Depending on the model, Senix sensors have one or two simultaneous switches. Each is independently adjustable. Computer-configurable models allow the switches to turn ON and OFF at different distances (hysteresis) or to be ON or OFF only when a target is within a specified switch window.

The hysteresis feature allows a single sensor to perform a complete control function, such as turning a pump ON at a low level and OFF at a high level to maintain a liquid level within limits. The switch window feature allows proximity sensing only within specific distance ranges.

Serial Data

Both RS-232 and RS-485 interfaces are available for most Senix sensors. All SensorView™ computer configuration is done through RS-232 or RS-485 communications. Other simultaneous outputs are usually also connected to the user’s equipment. The serial data interfaces provide the measured distance as an output to any compatible external device. The RS-485 interface is used to connect several sensors in a network that is monitored by a single communication interface.

At Senix, ultrasonic sensors are our only business! We routinely configure, modify and design ultrasonic products that meet special customer requirements. We have the expertise to develop and manufacture products for original equipment manufacturers (OEMs).

Senix has been designing, manufacturing and selling ultrasonic sensors since 1990, and has since introduced technical innovations like push-button TEACH and computer-configurable sensors. Let us know how we can put our knowledge into your products—contact the Senix team for product assistance or technical help.

Absolutely not! Push-button TEACH features provide all the functionality many users require. Our computer-configurable sensor models, however, offer greater ease of use, featuring flexibility and application visibility that many users find essential.

The features provided by SensorView™ software would not be possible without a computer. Once a sensor’s installation and setup are determined, its settings can be stored and duplicated easily and quickly using the computer.

Senix can also provide sensors pre-configured to your exact needs.

Selecting the right sensor range for your application depends on many variables, including target characteristics and the measurement environment. In liquid level applications, we recommend that you select a sensor range at least 25% greater than the maximum distance you are likely to measure.

When measuring dry materials or difficult targets, we recommend selecting a sensor range at least 50% greater than your maximum measurement distance.

Senix Customer Service can help you select the right sensor for your needs. Contact us today for product selection assistance!

Don’t forget to visit our Ultrasonic Sensor Selection Guide to learn about other important criteria in the selection process.

The ultrasonic beam angle in ToughSonic® sensors is typically 10-15° and is conically shaped. The real-world response to an off-angle target has a lot to do with the target size and orientation, and the sensitivity setting of the sensor.

Computer-configurable sensors can be adjusted to optimize detection of the desired target and ignore undesired targets that may fall within the sensor’s measuring range.

A common misunderstanding is that if the ultrasonic beam is larger than the target there is a problem. This is not true. It doesn’t matter if the beam is larger or reaches other objects in its path, as long as those objects do not reflect sound back to the sensor and are located farther away than the target of interest.

For example: a sensor can be mounted next to a wall or can measure inside a tube. The measurement will not be affected as long as the wall or tube surface is smooth, since no sound energy is reflected back to the sensor from the surface.

In computer-configurable sensors, the detection of undesired or off-axis objects can be affected by beam width, sensitivity adjustment, range adjustment, processing filters, and object masking.

Need technical help while configuring sensors in SensorView™? Contact Senix’s team for convenient assistance.