In this short article, we share a few guidelines and illustrations to help you select the most critical component of ultrasonic flowmeters – the ultrasonic transducer. Every flowmeter installation is different, which is why SoundWater offers a number of configurations for each of its flowmeter families: Cypress and Orcas. Selecting the correct transducer model will help your flowmeter to reliably measure flow.

The ultrasonic transducer is the part of the flowmeter that both transmits ultrasound into the pipe and fluid and receives it as the sound exits the pipe. It is important to select transducers that best match your pipe sizes and materials. This allows the sound to traverse the pipe and fluid most effectively and ensure good flow measurement. Below are guidelines to help with this selection.

Two illustrations will help with transducer selection. First, the general transducer size chart (Fig 1) displays four transducer options (-T304, -T310, -T410, -T420), as well as the ”recommended” and “possible” pipe size ranges for each. As you can see, there is overlap. In general, try to select the transducer with a recommended working range that will cover most of your applications.

The second illustration is a decision tree (Fig. 2), which guides you through the selection. Examples include: 

• If you are working with pipe below two inches in diameter, then in general you will always want to use the -T420 transducer which is designed specifically for smaller pipes.

• If you work with copper or brass pipe, select from either -T420 (small pipes) or -T410 (larger pipes).

• If you work with very large pipe (larger than 24 inches in diameter), then the lower frequency transducer-T305 would be best.

In addition to transducer selection, you also need to decide how transducers should be mounted on the pipe: direct vs. reflect mode.

• Direct Mode: The transducers are setup on either side of the pipe. This allows the sound to traverse the pipe only one time, shooting sound directly at each other.

• Reflect Mode: The transducers are mounted on the same side of the pipe, and the sound traverses the pipe twice, requiring a reflection off the backside of the pipe.

Reflect mode is often the default choice and easier to work with because there is just one piece. However, a direct mode should be used if you are working with pipes larger than 12” in diameter or the have internal pipe linings, high corrosion, or heavily particulated fluids.

We hope this helps and as always, please contact us if you have any questions or need more information. We look forward to talking with you about your flow application and helping you select the best transducer for your application.