What is an Ultrasonic Gas Flow Meter, and How Does it Work?


An ultrasonic flow meter is a device used to measure the flow rate of liquids and gases without the need for moving parts or contact with the internal fluid. Ultrasonic flow meters are widely used in various industries, including residential and commercial applications, natural gas, and compressed air. Accurate measurements of flow rates can help improve process efficiency, ensure product quality, and reduce energy consumption.

Ultrasonic gas flow meters use ultrasonic technology to measure the velocity of gas bubbles or suspended solids in a flow stream. Depending on the desired technology, these devices are designed to be installed inside or outside the pipe. Ultrasonic flow meters offer several advantages, including minimal maintenance and high accuracy. In this blog post, we will explore the different types of ultrasonic flow meters, how they work, and their various applications.

What is an Ultrasonic Flow Meter?

An ultrasonic flow meter is a device used to measure the flow rate of a fluid by utilizing ultrasonic technology. The meter measures the time it takes for ultrasonic waves to travel between two transducers on opposite sides of a fluid flow stream. By comparing the upstream and downstream transit times, the flow velocity and flow rate of the fluid can be calculated. Ultrasonic flow meters are typically non-intrusive and can measure the flow of various liquids and gases in various pipe sizes, making them useful in various applications.


How Ultrasonic Gas Flow Meters Work

Ultrasonic Technology

Ultrasonic flow meters operate on the principle of using ultrasonic technology to measure the flow rate of liquids and gases in pipes. The ultrasonic flow meter sends ultrasonic waves through the flow stream, which are then reflected in the meter by suspended solids, gas bubbles, and the internal pipe wall. The flow meter calculates the flow rate based on the time difference between the ultrasonic waves that travel upstream and downstream.


Types of Ultrasonic flow Meters

Technologies – Transit Time and Doppler Effect

There are two types of ultrasonic flow meters technologies: transit time and Doppler effect. Transit time ultrasonic flow meters are most common for inline ultrasonic flow meters. They use two transducers installed on opposite sides of the pipe. One transducer sends an ultrasonic signal upstream, while the other sends a signal downstream. The transit time of these signals is measured and used to calculate the velocity of the fluid.

Doppler effect ultrasonic flow meters are most common for clamp-on applications. They use one transducer that sends ultrasonic waves at an angle to the flow stream. The waves bounce off gas bubbles or solid particles in the flow stream, and the change in frequency is used to calculate the velocity of the fluid.


Ultrasonic Meter Installation Types

There are two different types of gas ultrasonic flow meters: clamp-on and inline. Each type of flow meter has its unique features and applications.

Clamp-on ultrasonic flow meters are non-invasive devices that can be easily installed without interrupting the flow process. Transducers are clamped onto the outside of a pipe to measure flow. Clamp-on meters are commonly used when pipes are too large to be cut or in applications where the fluid cannot be contaminated.

Inline ultrasonic gas flow meters, or insertion meters, are installed directly into the pipeline and use two transducers mounted opposite each other to measure the flow rate. This meter is most suitable for clean fluids and can handle higher flow rates. They have less than 0.2% uncertainty after flow calibration, making them the most precise meter type. Additionally, they have the greatest rangeability of any flow meter, and it would take approximately 3-5 differential meters to have the same range. They are also inherently bi-directional, with no moving parts, no pressure drops, and superior diagnostics.


Inline Gas Ultrasonic Meter Applications

Inline gas ultrasonic flow meters are versatile devices used in various applications. They are widely used in onshore and offshore production facilities, natural gas transmission pipelines, compressor stations, processing facilities, and city gates to measure the flow of gases accurately.

Inline gas ultrasonic flow meters are also helpful in industries that consume large volumes of natural gas as fuel or feedstock, such as power generation, refining, processing, and petrochemical industries.

Benefits of Ultrasonic Flow Meters

Ultrasonic flow meters have seen a remarkable 50% year-over-year growth in installations since the mid-1990s, making them a favored technology for fiscal and operational purposes in many transmission and distribution companies. This is due to their many benefits, including unparalleled accuracy that can be calibrated to less than 0.1%, a large turndown ratio typically exceeding 50:1, natural bi-directional measurement, and the ability to tolerate wet gas, which is crucial for production applications. Additionally, ultrasonic flow meters are non-intrusive, resulting in no pressure drop, require minimal maintenance as they have no moving parts, and offer fault tolerance, retaining accuracy even if sensors fail.

The Best Inline Ultrasonic Gas Flow Meters – Rosemount Analytical’s 3410 Series

Rosemount 3410 Series Ultrasonic Flow Gas Meter

Rosemount Analytical’s 3410 Series is considered one of the best ultrasonic gas flow meters available. This series offers high accuracy, advanced flow meter diagnostics, and great rangeability. Unlike other flow measurement devices, it has no moving parts, which eliminates pressure loss and enhances its reliability.

The 3410 gas ultrasonic flow measurement products are utilized worldwide for critical gas measurement applications, including custody transfer, allocation measurement, check metering, leak detection, and inventory control. They are commonly installed in onshore and offshore production facilities, natural gas transmission pipelines, compressor stations, processing facilities, and city gates. Additionally, these products are particularly useful for heavy natural gas consumption applications, such as power generation, refining, processing, and petrochemical industries.


Rosemount Gas Ultrasonic Flow Meter Uses

Rosemount JuniorSonic 3412 Two-Path Gas Ultrasonic Flow Gas Meter

Rosemount’s 3410 series gas ultrasonic flow meters have several uses due to their accuracy, reliability, and rangeability. One of the most common is the allocation of gas and check metering. The meter measures gas flow through pipelines to different users to ensure that each user receives their allocated amount of gas. This is particularly important in the oil and gas industry, where accurate gas flow measurement is critical for revenue generation and profit optimization. The Rosemount JuniorSonic 3411 and 3412 One-Path and Two-Path Gas Ultrasonic Flow Meters are perfect for allocation and check metering.


Rosemount SeniorSonic 3414 Four-Path Gas Ultrasonic Flow Meter

Another common use for these meters, especially Rosemount’s SeniorSonic 3414 Four-Path Gas Ultrasonic Flow Meter, is custody transfer, which involves the transfer of gas from one party to another. In such applications, the accuracy of the flow measurement is of utmost importance to ensure that both parties receive the correct amount of gas and that billing is done correctly.


Rosemount 3415 4+1 Duel-Configuration Gas Ultrasonic Flow Meter

Measurement verification and blockage detection are important uses for Rosemount’s 3415 and 3416 4+1 Dual-Configuration Gas Ultrasonic Flow Meters. These meters can be used to monitor the performance of other meters installed in the system, as well as to detect blockages or other obstructions that may be affecting the flow of gas through the pipeline. This helps to ensure that the system is running efficiently and safely.


Finally, redundancy is another important use for these ultrasonic gas meters. In critical applications such as oil and gas pipelines or power plants, having redundant flow meters is essential to ensure that gas flow is not interrupted in case of a malfunction or breakdown of one of the meters. In such cases, the flow meter can act as a backup and ensure that gas flow is maintained without any interruption. Rosemount’s 3417 4+4 Dual-Configuration and 3418 Eight-Path Ultrasonic Flow Meters are the premium tiers for redundancy and premium accuracy.


Overall, the different uses of Rosemount’s 3410 series inline gas ultrasonic meters make them an essential tool in the oil and gas industry, power generation, and other applications that involve the flow of gas through pipelines.


Installing and Operating an Ultrasonic Flow Meter

Proper installation techniques:

  1. Select the appropriate meter for the specific application based on the fluid type, pipe size, and operating conditions.

  2. Choose the appropriate installation method: clamp on ultrasonic flow, open-channel, or in-line.

  3. Ensure proper positioning of the ultrasonic transducers to obtain accurate measurements. The transducers should be installed perpendicular to the pipe axis and aligned with each other to ensure an accurate ultrasonic signal.

  4. Properly mount and secure the transducers to prevent movement or displacement that could affect measurements.

  5. Ensure the pipe wall is clean and free from any obstructions or debris that could interfere with the ultrasonic signal.

  6. Calibrate the flow meter according to the manufacturer’s instructions to ensure accurate measurement.

  7. Contact Cherokee Technical Solutions for more assistance with startup and commissioning.


Maintenance and troubleshooting tips:

  1. Regularly inspect and clean the transducers to prevent the buildup of any deposits that could affect measurements.

  2. Check the signal strength periodically to ensure the ultrasonic signal is strong enough for accurate measurement.

  3. Perform periodic zero and span calibration to ensure accuracy.

  4. Monitor for any abnormal readings or fluctuations and investigate any issues that may arise.

  5. Consult the manufacturer’s instructions for any specific maintenance requirements or troubleshooting tips.

  6. Contact Cherokee Technical Solutions for your routine maintenance and on-demand field service needs.


In conclusion, ultrasonic gas flow meters are a versatile and accurate method for measuring flow in various applications. They offer advantages over other meters, such as minimal maintenance and no moving parts. Rosemount Analytical’s 3410 Series is one of the most reliable and accurate ultrasonic gas flow meters on the market today. The different uses for these meters make them invaluable in various industries such as oil and gas, power generation, etc., where accuracy and reliability are essential. Whether it’s for allocation or check metering, custody transfer measurement verification, or blockage detection – this series has you covered with its rangeability, accuracy, and advanced diagnostics capabilities.