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Ever wondered how the ultrasonic flow meter working principle can help you deliver an impressive ±1% accuracy rating? Yes, it's true, and that's why this device stands out as the top choice for precise flow measurement. To know more about the Ultrasonic flow meter technology and how it helps us gauge the flow velocity of predominantly clean liquids, regardless of whether the system is active or shut down, we will have to delve deeper. In this article, we will have an understanding of what exactly this device is, what the ultrasonic flow meter's working principle is, its types, and its various applications. So let's get started.

What is an Ultrasonic Flow Meter?

Ultrasonic Flow Meter
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Utilizing ultrasonic waves, an ultrasonic flow meter gauges the flow of liquids or gases by transmitting signals across a pipe. The combination of these waves and the flow velocity accurately determine the flow rate. Ultrasonic flow meters influence the sound waves of the liquid, impacting factors such as density, viscosity, and temperature. 

The ultrasonic flow meter accuracy rate is outstanding. In addition to that, they boast a very high turndown ratio, allowing them to effectively handle a broad spectrum of flow rates within a single meter. Despite their variable pricing, they operate without moving parts, which contributes to their low maintenance costs.

What is the Ultrasonic Flow Meter Working Principle?

Have you ever noticed a passing car where its sound remains constant, but your perception of its incoming sound changes? This effect is attributed to the principle of ‘transit time,’ a phenomenon also harnessed by ultrasonic flow meters to measure flow rates.

So, to understand how does ultrasonic flow meter works, it's important to know that the working principle of the ultrasonic flow meter is the run-time difference. To elaborate further, the ultrasonic waves in the fluids or gases (media) running through the pipe are affected by the flow rate. There are two sensors mounted in both the inline and clamp-on models. In inline, these are mounted opposite each other in the pipeline, and for the clamp-on models, these are fixed on the pipeline. These sensors act as both transmitters and receivers of ultrasonic acoustical signals. When there's no movement in the media, both signals have identical run times. However, in the presence of flow, the signal against the flow exhibits a longer run-time than the one with the flow. This run-time difference, proportional to the flow rate, is processed by a microprocessor to provide a measurement reading.

Hence, in essence, ultrasonic technology utilizes the variation in running times between ultrasonic waves in a medium influenced by the flow speed to measure the flow meter.

Also Read: Understanding The Basics: How Flow Meter Operates?

What are the Types of Ultrasonic Flow Meters?

While there are scores of ultrasonic flow meter models with slight variations, they can be broadly categorized into two main types based on installation and operating principles.


The categorization as per the installation methods would be:

  • Inline Ultrasonic Flow Meters: These instruments feature built-in transmitters directly fitted into piping systems via connections.
  • Clamp-On Ultrasonic Flow Meters: Also known as portable or strap-on meters, these have transmitters mounted externally on the pipe. 

Operating Principles

From a technological standpoint, ultrasonic flow meters can be classified into two types based on their operating principles:

  • Doppler Principle: This principle gauges fluid velocity by measuring the frequency shift of sound waves scattered by particulate matter.
  • Transit Time Principle: It determines flow speed by measuring the time for ultrasonic pulses to move through the fluid, converting it to flow rate.

What are the Applications of Ultrasonic Flow Meter?

Ultrasonic flow meters offer invaluable solutions across a diverse range of applications, with newer clamp-on models extending their utility in areas where other technologies face compatibility challenges. Some of the applications of ultrasonic flow meters are as follows.

Widespread Industrial Utilization

In power plants, these meters optimize fluid flow, while in water and wastewater management, they ensure precise measurement and control. Also, ultrasonic flow meters contribute to efficient fluid flow in facility management and enhance operational effectiveness in the chemical industry. Additionally, they play an important role in maintaining accurate liquid flow in the dynamic environment of the food and beverage industry.

Media Compatibility

Ultrasonic flow meters demonstrate remarkable compatibility with specific media types, making them suitable for applications where other flow technologies may face limitations. They excel in handling diverse liquids, including sanitary, corrosive, and abrasive ones. Certain models are specifically designed to handle the challenges posed by cryogenic liquids (fluids with boiling points below 90 degrees C). In addition to that, they demonstrate efficient performance in applications involving petroleum-based fluids.

Technology-Dependent Media Compatibility

The compatibility of ultrasonic flow meters with various media types also depends on the specific technology employed—whether Doppler or Transit-time serves as the operating principle for the meter.

What are the Advantages and Disadvantages of an Ultrasonic Flow Meter?

Here are some of the ultrasonic flow meter advantages and disadvantages to help you decide if it suits your needs more or not.

Advantages of Ultrasonic Flow Meters

  • High Accuracy: Ultrasonic flow meters are generally known for their high accuracy, particularly in reading low flow rates.
  • No Moving Parts: Ultrasonic flow meters have no moving parts, ensuring a longer service life by avoiding wear and tear.
  • Minimal Maintenance and Low Operating Costs: These meters require minimal maintenance and boast low operating costs.
  • Good Dynamic Response: Ultrasonic flow meters provide an excellent dynamic response, enhancing their effectiveness in various applications.
  • Versatility with Non-Conductive Media: They excel in measuring non-conductive media and serve as an excellent alternative to magnetic flow meters requiring conductive liquids.
  • Low-Pressure Drop: They offer a low-pressure drop, making them energy-efficient.
  • Chemical Compatibility: Many models are chemically compatible with various substances, expanding their applicability.
  • Handling Dirty Media: Ultrasonic flow meters can handle dirty media, surpassing certain technologies with limitations.

Disadvantages of Ultrasonic Flow Meters

  • Higher Initial Cost: Depending on application demands and variables, ultrasonic flow meters might have a higher initial cost.
  • Sensitive to flow profile: Accurate measurements face challenges in non-ideal flow profiles, such as swirls or turbulent flow.
  • Incompatibility with Certain Liquids and Air Bubbles: The presence of holes or air bubbles in the pipe can also render ultrasonic flow meters ineffective.
  • Costly Audible Parts: Components responsible for producing audible signals in this meter can be expensive, contributing to overall cost considerations.
  • Professional Maintenance Requirement: Due to the ultrasonic flow meters complexity, you can not perform DIY repair work on them. They require professional expertise for maintenance and repair, adding to operational costs.
  • Limitations in Measuring Large Suspended Solids: These meters face challenges when measuring flow in rusty cement or concrete pipes.

How do you install Ultrasonic Flow Meters?

The installation process for an ultrasonic flow meter is contingent on the specific type of meter being utilized. In the case of an inline version, the meter must be seamlessly integrated into the piping system through securely sealed connections. It's crucial to adhere to upstream and downstream distance requirements during the installation of an inline ultrasonic flow meter. Maintaining sufficient space from any objects that could disrupt the flow profile is essential. Reference the installation manual for your specific flow meter model, as requirements can vary.

In contrast, installing a clamp-on ultrasonic flow meter proves significantly more straightforward, contributing to the growing popularity of this ultrasonic flow meter type. Transmitters are affixed to the external circumference of the pipe using various strapping methods. Ensuring that the pipe possesses acoustical properties conducive to the proper functioning of the ultrasonic principle of measurement is paramount.

Also Read: The Ultimate Guide To Flow Meter Installation For Best Accuracy

Why should you choose Ultrasonic Flow Meters?

While ultrasonic flow meters and magnetic flow meters share similarities in pricing, the distinctive advantage of ultrasonic flow meters lies in their ability to measure non-conductive media. Unlike magnetic flow meters, which require a minimum level of conductivity in the media, ultrasonic technology extends compatibility to various media types that may not work with magnetic flow meters.

One notable area where ultrasonic flow meters outperform magnetic flow meters is the availability of clamp-on versions. These versions offer substantial cost savings, particularly in large bore applications, and are adept at handling media characteristics that might pose compatibility challenges for inline flow meters or magnetic technology. The clamp-on ultrasonic flow meter models further provide the advantage of no media contact, enabling the measurement of media that may be inaccessible to other technologies.

Given that ultrasonic flowmeters are proven to be a more appropriate choice on a variety of grounds, at Kritsnam we have spent years designing and developing the Dhara Smart Ultrasonic flowmeter. In recent years it has become a popular choice for groundwater extraction, water auditing for business, smart irrigation and even in tracking domestic water usage.


In summary, ultrasonic flow meters prove to be optimal choices for liquid and gas applications, including water. The distinctive advantages include their ability to achieve high accuracy across a broad spectrum of flow rates, encompassing both low and high flows. Furthermore, certain time-saving installation features of ultrasonic flow meters enhance operational efficiency. Notably, these flow meters remain impervious to external noise, ensuring reliable performance in various environments. Overall, the versatility and efficiency of ultrasonic flow meters, underscore their significance in liquid measurement applications.

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