Dayu Electronics: Ultrasonic Flowmeter Transducer Frequency Selection Guide

In industries such as petroleum, chemical, urban water supply, and gas transmission, accurate and stable flow monitoring of large-diameter pipes (2.00 m to 10.00 m) is a core part of energy management and process control. Dayu Electronics' ultrasonic flowmeter, with its non-contact and no-pressure-loss advantages, is the preferred choice for such applications. However, given such a wide range of pipe diameters, selecting the appropriate transmitting frequency for the ultrasonic transducer is the primary technical decision to achieve high-reliability measurement.

Medium and flow velocity determine frequency selection

The choice of transducer operating frequency is by no means merely a matter of higher or lower values; it is essentially a comprehensive trade-off among the ultrasonic propagation characteristics in the specific medium, the measurement distance (pipe diameter), and the dynamic response capability (flow velocity). Higher frequencies mean shorter wavelengths and better directivity, but greater attenuation during propagation in the medium; lower frequencies provide stronger penetration and longer measurement distances, but may differ in instantaneous resolution of flow velocity changes.

Scenario 1: Measuring water flow (taking relatively clear water as an example)

Water, as a typical liquid medium, attenuates ultrasonic waves relatively little, offering a wide range for frequency selection. For large pipes of 2–10 meters, frequency selection needs to focus on the flow velocity range:

Low-to-medium flow velocity conditions (<2.00 m/s): At such flow velocities, the fluid state is relatively stable. It is recommended to use transducers with frequencies from 500 kHz to 200 kHz. Higher frequencies (e.g., 500 kHz) help form a more focused acoustic beam, improving measurement resolution and anti-interference capability at low flow rates, ensuring stable signal capture even in very large pipe diameters.

Medium-to-high flow velocity conditions (2.00 - 10.00 m/s): When flow velocity is higher, the fluid may contain more bubbles or turbulence. To ensure sufficient penetration and stability of the ultrasonic signal in complex flow patterns, it is recommended to use transducers with frequencies from 100 kHz to 200 kHz. This frequency range maintains good directivity while providing stronger attenuation resistance and environmental adaptability, effectively coping with the challenges posed by high flow velocities.

Scenario 2: Measuring gases (e.g., air, natural gas)

The acoustic impedance of gaseous media is much lower than that of liquids; ultrasonic waves attenuate greatly when propagating in gases, and the sound velocity is significantly affected by temperature and pressure. Therefore, gas measurement, especially with large pipe diameters, imposes stricter requirements on transducer frequency selection.

For pipes with diameters of 2 to 10 meters, within the typical flow velocity range (0.10 - 10.00 m/s), low-frequency transducers around 40 kHz become a common and reliable choice. The reason is that low-frequency ultrasound attenuates significantly less than high-frequency waves in gases, enabling it to penetrate large pipe diameters and ensuring that the opposite-side transducer can receive a signal of sufficient strength. At the same time, this frequency balances measurement sensitivity and system signal-to-noise ratio requirements, making it a mature technical solution for gas media measurement challenges.

In summary, selecting the transducer frequency for large-diameter flowmeters must adhere to the principle of "choose according to the medium, select according to the flow velocity." For water flow measurement, the frequency can be optimized within a wide band based on flow velocity, while gas measurement usually requires prioritizing low-frequency solutions to ensure signal strength. Correct frequency selection is the foundation for ensuring the accuracy, stability, and lower measurement limit of the entire measurement system.

Dayu Electronics offers a range of transducer products with frequencies from 40 kHz to 500 kHz and various structural forms, along with a professional technical support team that can assist you in conducting systematic analysis and selection based on specific medium properties, pipe conditions, and process requirements, providing a reliable sensing core for your critical flow measurement points.