Ultrasonic Level Sensors

Ultrasonic sensors emit high frequency sound waves from the transducer. These sound waves then reflect off the liquid surface you are trying to measure. Once the wave returns to the transducer, the ultrasonic level sensor then measures the time that the wave took to reflect off the liquid’s surface and converts the measurement into a calculated distance.

How Does An Ultrasonic Level Sensor Work?

Ultrasonic sensors work by sending sound waves that echo off of a target and return to the transmitter. The ultrasonic sensor calculates the distance to the target based on the amount of the time that it took for the sound wave to return to the transmitter. The term ultrasonic means above human hearing, or any sound wave above 20 kHz. This method is quite accurate, and we’ve developed a line of sensors with an accuracy of 0.25% of detected range.

Because the speed of sound is constant, under fixed atmospheric conditions, the time from the sound burst to the return is measured and translated into a distance. The ultrasonic level sensor’s microprocessor calculates the distance and converts it to a level indication, volume measurement, or a rate of flow. It can also compensate for temperature, and filter the signal.

Common uses for ultrasonic level sensors are level, volume, and flow monitoring. Other uses include presence or absence detection, and object dimensioning.

Ultrasonic level sensors are typically quite small, low maintenance, and easy to ship and install. Each of our ultrasonic sensors have a microprocessor, which allows for more advanced control. In addition, they do not come in contact with the target substance, which avoids build-up and damage.

Ultrasonic sensors require an unobstructed air column between the sensor and the target. Anything that deflects or absorbs the signal, or acts as a false surface, may cause erroneous readings. This can result from physical obstructions, excessive foam, heavy vapors, thick dust and light powders.

To ensure your ultrasonic level sensor is able to properly measure the surface, a stilling pipe can be used to contain or guide the signal around obstructions, or to lessen surface foam. A more powerful sensor can also be used to strengthen the signal. However, our continuous float level transmitters and submersible pressure transducers may be best in these scenarios.

What Are Ultrasonic Sensors Used For?

Ultrasonic Sensor Features

Our ultrasonic level sensors are known for their field programmability. Within minutes, you can perfectly match your sensor’s parameters to your application, giving you unparalleled performance.

Most of our ultrasonic sensors are designed for use in level applications with ranges from as little as 4 inches to as much as 50 feet. They are used both indoors and out, capable of monitoring in cold and hot weather. Automatic temperature compensation is standard in each model.

Programming our ultrasonic level sensors is relatively easy, and is usually done well in under 30 minutes. This process is fairly straightforward, and our tech support is ready to help if you run into trouble.

There are three main settings you can adjust:

Pulse Strength & Sensitivity
Filtering & Response Time
Output & Trip Points

Pulse Strength & Sensitivity

The pulse strength control lets you fine tune sound wave bursts for optimal detection for your application. The sensitivity setting gives you control over how hard the sensor will listen for echoes. To put it simply, pulse strength is like volume control on a speaker, while sensitivity is like volume control on a hearing aid.

Adjusting the two is important. You want your pulse strength only as high as is necessary to get a good return signal. If you leave it on high all the time, it will wear down faster, just like a speaker can be blown out by too much volume. Unlike a speaker, the ultrasonic transducer - the part that makes and receives the sound waves - won’t blow out, but will wear down over time.

So if you have your pulse strength ramped up as high as you can just to get a good return signal, it means your sensors isn’t powerful enough. You need a longer range ultrasonic so you can keep your pulse settings at a happy medium. This will give you a better signal and increase the lifespan of your level sensor.

Sensitivity settings are all about receiving the echoes. If you have to turn up your sensitivity too much, you’ll start to pick up unwanted echoes and erroneous readings. Having to keep your sensitivity too high is a symptom of either a low pulse strength setting, a target that absorbs or dissipates your signal, or a sensor with too short a measurement range.

Balancing pulse strength and sensitivity is crucial to a reliable measurement and a durable sensor. The good news is, you’ll likely be able to use AutoSense, which automatically adjusts pulse strength and sensitivity to optimum settings.

Filtering & Response Time

Filtering out unwanted echoes with your ultrasonic level sensor is easy with a few different settings. You can control the maximum and minimum detection distances, the averaging of your readings, and the response speed to changing levels.

Setting a maximum and minimum detection distance simply causes the sensor to ignore any echoes outside of that range. The minimum detection distance is really controlled by lengthening your blanking distance, which is a short distance right in front of the sensor face where nothing can be detected (see individual sensor specifications). The maximum distance setting is helpful if you ignore static or mobile objects in the distance.

Averaging your readings is a way to smooth out your level changes. You’ll need this feature unless you have a very slow moving, perfectly still surface to detect. Any amount of turbulence or uneven movement on the surface, and averaging becomes very valuable. Simply tell the sensor how many samples (singular readings) you want to average. The more samples you choose, the greater the smoothing effect.

Controlling the response speed to changing levels is very helpful for filtering out a lot of noise. This setting is called a window, or a set distance of your choosing in front of and behind the current distance reading. This is a moving window that follows the current accepted reading. Along with the window, you’ll set the number of samples the sensor needs to detect out of the window before it validates as a new level. Essentially, you’re causing your sensor to double check the changes in the level before it serves it to you as an output.

Both averaging and the windows settings can speed up and slow down response time. If you have a fast moving target, then you’ll want to be careful here. Lower averaging and a looser window is required to keep your readings caught up with rapid changes.

Output & Trip Points

Setting up your output on our ultrasonic level sensors is a simple process of defining your maximum and minimum output values. But it doesn’t stop there! Our most popular series have the option to include 2 built in NPN trip points.

Trip points help you control pumps, alarms, and valves easily. Other manufacturers don’t include trip points in their ultrasonic level sensors, forcing you to spend another couple hundred dollars on a module. We not only offer them built into the sensor, but we offer them at no additional cost.

Feature Rich vs Feature Starved

Some of our competitors want you to believe that their lower cost ultrasonic level sensors are just as good as our higher quality line. The fact is, they don’t allow the programming of your sensor like we do. This means that you’ll never know if their ultrasonic sensor will work for you. If it does, you lucked out. If it doesn’t, there’s nothing you can do about it.

Having the programming options on one of our ultrasonic level sensors ensures you can get the performance you expect.

Ultrasonic Level Sensor Applications

From time to time, we get some customers who try some very interesting things with ultrasonic sensors - even if we express some skepticism. They’ve been used on everything from race cars to apple harvesters, some more successfully than others. But most of our ultrasonic level sensors are either used for liquid level, open channel flow, or for presence detection and object profiling, where they perform very well.

Liquid Level

The most popular application for ultrasonic level sensors is measuring the level in a body of liquid, be it in a tank, well, pit, or lake. If the container is linear, then inferring a volume measurement is easy. In non-linear containers, a strapping chart is often used to adjust the reading to a volume as level rises and falls.

Our ultrasonic level sensors are quite accurate (0.25% of detected range), and suitable for most measurements outside of custody transfer applications. Most of our ultrasonics are designed specifically for level measurement. Refer to the specifications to make sure you find a sensor that will work well for you.

Solid Level

Another very popular application for ultrasonic sensors is solid level detection. This differs dramatically from liquid level detection because solids don’t provide a flat, hard target. The target is often uneven and soft. However, ultrasonic sensors still do a good job much of the time.

The trick is really to use an ultrasonic sensor with double the needed range. This gives you a much stronger signal that will provide a better echo for your sensor to measure. You may also need to angle the mount of the sensor to be perpendicular to the angle of repose.

Level measurement with solids has always been difficult. And while technologies new and old promise optimum performance, ultrasonics will remain a staple for continuous non-contact measurement.

Avoid using ultrasonic level sensors on light powders or especially dusty environments. The softness of light powders will absorb most of the sound signal, while dust will dissipate the signal in the air before it can return to the sensor. You may still opt to use an ultrasonic in a dusty environment if you’re willing to wait for a good level reading once the dust settles.

Open Channel Flow

Another great fit for our ultrasonic sensors is open channel flow. Open channels are a primary means of transporting, filtering, and metering water. Open channel flow monitoring is used in water treatment plants, in environmental monitoring, and in irrigation canals.

Our ultrasonic level sensors are commonly paired with an appropriate controller for flow calculations over open channels. They are preferred for their ruggedness in outdoor environments where reliability is paramount. Several of our models are a good fit for this application.

Presence Detection & Object Profiling

There are many technologies designed for detecting objects and controlling the movements of machines and robotics. Ultrasonic sensors are well suited for some of them. For example, did you know the automatic car wash industry relies heavily on ultrasonic sensors for detecting vehicles and controlling the movement of brushes?

Ultrasonic level sensors are good in many of these applications because of their ability to handle adverse conditions. Object detection required in dirty or wet environments where the targets are fairly slow moving is potentially a good fit for ultrasonic sensors. Our IRU-2000 series is designed for these applications.

FAQs