There’s a myriad of ways to measure liquid level in industrial settings. One of the most popular tools for the task are ultrasonic level sensors. Originating with sonar technology used to detect submarines, ultrasonic is now commonplace in industries from agriculture to oil and gas. But why are these sensors so ubiquitous?
Riding the (Sound) Wave
To understand why ultrasonic sensors are so popular, let’s first look at how they work. Ultrasonic sensors measure liquid levels by leveraging sound waves. They’re mounted above the liquid’s surface and send out high-frequency pulses. Here’s a breakdown of the process:
- Emission: The sensor emits a high-frequency acoustic pulse from its transducer. This pulse travels through the air gap above the liquid surface.
- Reflection: When the pulse reaches the liquid surface, it reflects back toward the sensor. The time taken for the pulse to travel to the surface and return is crucial.
- Time of Flight: The sensor calculates the time of flight (TOF) for the pulse. Essentially, it measures how long it takes for the pulse to make the round trip.
- Conversion: Using this TOF data, the ultrasonic sensor determines the distance from the sensor to the liquid surface. This distance corresponds to the current level within the tank.
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The Benefits of Ultrasonic
Ultrasonic began being used practically in industrial applications around the mid-1950s. This is thanks in large part to a surge in sonar development—a silver lining after the tragic sinking of the Titanic in 1912. Since its inception, ultrasonic measuring has become a popular choice in various industries. Here are key advantages of the technology:
- Non-contact measurement. Ultrasonic sensors don’t require physical contact with the liquid—particularly useful for measuring corrosive or hot liquids while preventing contamination and potential sensor damage.
- Extended range. Individual sensors can be built to measure a great range of distances, from a few inches to 50+ feet.
- Easy installation. Installing the sensors is straightforward. There’s no need for physical contact with the liquid, so complex mounting or submersion arrangements can be avoided.
- Versatile. A liquid’s color, transparency, and viscosity (informally, “thickness”) do not impact sensor measurements.
- Cost-effective. Other technologies, like radar, may offer similar benefits—but they can be more costly and complex. Ultrasonic is generally more accessible due to durability and low maintenance requirements.
Transducer or Sensor?
Usually, a transducer converts a signal in one form of energy to another. A sensor detects events or changes and sends that information to other electronics, such as an IoT controller.1
Common Ultrasonic Sensor Applications
| Industrial Processes Measuring water levels in industrial tanks, boilers, and processes is essential for operational efficiency, safety, and quality control. Industries such as plastics, food and beverage, and pharmaceuticals benefit from real-time monitoring to prevent overflows and mitigate damage. | Environmental Monitoring Monitoring water levels in rivers, lakes, and wetlands helps protect ecosystems and respond to or prevent flooding. Real-time data aids in disaster preparedness and response. |
| Agriculture Monitoring liquid levels in agricultural tanks ensures efficient irrigation, preventing under- or over-watering and aiding in inventory management of fertilizers. | Water Management Water treatment plants, reservoirs, and distribution systems rely on tank level data to maintain consistent water flow and manage storage capacity. |
| Oil and Gas In the oil and gas industry, tank level monitoring ensures accurate inventory management, preventing shortages or excesses. | Chemical Plants Non-contact ultrasonic allows for accurate level measurement without needing to use specialized sensors that come into direct contact with potentially corrosive chemicals.2 |
Ultrasonic Sensors and IoT Controllers in Tank Level Monitoring
For example, the MNU-3434 is capable of monitoring up to 40 feet.
Using ultrasonic sensors to measure liquid level in a tank is one part of the equation. The other component is executing logic. This can be done by relaying sensor data directly to a central system, or SCADA, which can execute commands. However, this form of one-way communication can be limiting. Another option is to connect an IoT controller directly to the sensor.
An IoT (or micro) controller can make logical decisions at the edge, executing conditional tasks using its own smarts. This offloads tasks from the central system and adds reliability in case of a failure—the controller can continue operating even if the central system goes down.
A controller can read information from ultrasonic sensors, send commands, and control actuators (like valves and pumps) based on predefined logic to maintain the desired level of liquid within the tank. This doesn’t have to add complexity or a lot of overhead, either. ControlByWeb® IoT controllers include a no-code embedded UI to build logical processes through intuitive drop-down menus in an if-this-then-that flow. They’re a lot more affordable than a traditional controller and much easier to set up.
Product Spotlight: X-412™ 4-Channel Relay & Analog Input Module
The ControlByWeb X-412 no-code controller features four analog inputs that can connect with a wide variety of sensors. It’s capable of advanced control logic and can convert data to send to external systems. The 400 Series platform is integration-ready, supporting HTTP GET, XML, Modbus, MQTT, and more.
Common Liquid Sensors
Ultrasonic sensors aren’t always the best choice for a given application. Foam and bubbles can cause issues with the ultrasonic wave, for example. Here are common sensors used to measure liquid level or hydrostatic pressure and how they compare to ultrasonic.
Ultrasonic Level Sensors
Great sensors for clean water tanks, flumes, and weirs. They’re proven to be reliable in controlled environments, cost-effective, and accurate. However, ultrasonic level sensors aren’t suitable for tanks with interior obstructions or variables like foam and vapor.
Non-Guided Radar Level Sensors
These sensors are newer compared to ultrasonic level sensors and can be more accurate, especially when handling process variables. Generally, non-guided radar level sensors are more expensive and more complex to tune.
Hydrostatic Pressure Transmitter
These transmitters, also known as submersible pressure sensors, can be lowered to the bottom of a tank to convert water column pressure to other units of measure. They’re ideal for deep wells and water towers where distance may be too great for non-contact measurement.
Point-Level Switches
Float, capacitive, and other level switches are inexpensive and common for redundant level control. They don’t provide the data or fine-tuned control possible with continuous measurements, PID loops, VFDs, etc., but level switches are still widely used for their reliability.
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The Advantage of ControlByWeb® Edge Controllers in Tank Level Monitoring
ControlByWeb no-code controllers stand out in tank level monitoring applications thanks to robust I/O and communication options combined with an easy-to-use embedded UI. They have proven to be reliable, flexible, and able to handle complex control tasks efficiently, making our controllers a go-to option for integrators.
For help with your industrial application, contact our team or schedule a 15-minute product demo.
Tailor-Made Solutions
At ControlByWeb, we’re happy to work with you to develop custom I/O solutions. If you need a particular setting enabled by default, white labelling, or other personalized solution, please contact us.
References
- (n.d.). Difference Between Transducer and Sensor. BYJU’s. https://byjus.com/physics/difference-between-transducer-and-sensor/
- Asher, R. C. (1983). Ultrasonic sensors in the chemical and process industries. Journal of Physics E: Scientific Instruments, 16(10). https://doi.org/10.1088/0022-3735/16/10/004
