Today, we will discuss where can we use an Ultrasonic Level Transmitter. However, before that, we will touch upon how does an Ultrasonic Sensor works and what difficulties we face while selecting a device.
We have many methods we can use for non-contact level measurement, each with benefits and limits. Radar, for example, offers great accuracy – for a wallet-pinching price. Ultrasonic sensors, however, cost less and are easy to install and use, making them the most popular non-contact method for level measurement.
Ultrasonic level sensors use the “Time of Flight” principle to measure level. The device sends sound waves at a frequency higher than humans can hear, from 20 kilohertz to one gigahertz.
These waves bounce from the surface of the product, creating an echo that goes back to the sensor. Then, the sensor calculates the time the echo took to return to find out the level. It works in both: fluids and solids.
This principle seems simple. Yet, it´s important to keep in mind some technical aspects for getting accurate measurements:
- Air temperature can affect sound velocity. The hotter the air, the faster the sound travels. So, an integrated temperature sensor can help you compensate for this effect. The space between the sensor and liquid must be at a uniform temperature to give you accurate data.
- Your product needs a certain density to reflect ultrasonic waves. Sound travels faster through the air than through solids and liquids, so a significant difference in density between the air and your product results in a good signal.
- The sensor has a blocking distance where it can’t read properly, so you must include that in your calculations. For more information on blocking distance, you can also read our article on this.
- Different products affect sound waves differently. For example, helium atoms are less massive than air molecules and so at a given temperature, sound travels faster in helium than air. This is the reason when you inhale helium from a balloon; the pitch of your voice rises so dramatically.
- The profile of the liquid surface is an important point to consider. If the profile is turbulent, it results in foam. The readings are deflected due to foaming.
- Obstructions in tanks can cause multiple and false reflections, but nowadays, signal processing helps to ignore these problems. This issue can be eliminated up to a certain limit. However, Radar level transmitter can a solution to this issue.
- The level measurements get affected by the presence of vapor or steam above the measuring surface. This is because vapor interrupts the transmission and reflection of an ultrasonic signal.
- Vacuum applications are also not possible with an Ultrasonic Sensor. The ultrasonics cannot travel through empty space, they need medium like gas, liquid or solid to travel and take measurements!
As long as you take these factors into account, you can use ultrasonics in many industries and applications. Let’s go over a few.
Water and Wastewater Applications
The water and wastewater industry strongly favors ultrasonics because it helps with pump control, cycling and monitoring, overfill protection and more. In fact, ultrasonics have become the standard for most liquid level requirements.
Water and Wastewater applications use open channel flow monitoring technique for measurement of flow in various water systems. In this technique, flow rate of water is determined by measuring the height of water with the help of an Ultrasonic Level transmitter.
ABB- LST400 Ultrasonic Level Transmitter
Krohne- OPTISOUND 3020 Ultrasonic Level transmitter
Endress+Hauser- FMU30 Ultrasonic Level transmitter
In the chemical industry, Ultrasonic Transmitter applications include level measurements for corrosive liquids, fuel glues, resins, paints, rubbers, and plastics. The chemical industry often measures potent products, so you’ll need a non-contact level measurement.
Ultrasonics work excellently on storage tanks for corrosive materials such as hydrochloric acid (HCl), sulphuric acid (H2SO4), and caustic soda (NaOH).
Still, you should make sure your sensor material is chemically compatible. Many ultrasonics come with wetted materials made of PVDF.
ABB- LST10 Ultrasonic level transmitter
Senix- ToughSonic CHEM Models Ultrasonic sensor
Magnetrol- Echotel® Model 338 Ultrasonic level transmitter
Food and Beverage Applications
Ultrasonics appears this industry to measure grains, juices, powders, and more bulk solids in silos. But here, the sensors must meet hygienic requirements:
- The wetted parts must use certain materials that remain smooth and easy to clean. Buildup may ruin the product as well as the readings
- The sensor must meet the clean-in-place (CIP) temperature requirement. A hygienic cleaning cycle reaches up to 120 ˚C, so the sensor must withstand that heat for the length of the cycle.
- Sometimes, products can generate dust or noise that interferes with the signal. Choosing a highly sensitive sensor can eliminate this issue.
Endress+Hauser- FDU91F Ultrasonic sensor
Siemens- 7ML1201 Ultrasonic level transmitter
Solid Applied Technologies- MonoScan Ultrasonic Continuous Level Measurement Device
As a non-contact level transmitter, ultrasonic sensors make a good choice for wastewater, corrosive liquids and more. Ultrasonics are simple, low-cost devices that measure accurate and reliable data without affecting your product.
Also, there are some limitations to Ultrasonic Transmitter, which can be overcome by Radar Level Transmitter.
To know more about such transmitters, you can Ask Alex!