EVM430-FR6047: Ultrasonic Design Center: Calibrating clamped-on transducers to work with metal pipe

Hello Wojciech,

Clamp on metering does present some challenges due to the attenuation of the signal and signals riding along the pipe.  You also need to be sure that you have good clamping and couplant between the transducer and pipe.  Mechanical design is key here.    

I have done some evaluation using PVC pipes which do not have as much attentuation as a metal pipe.  For this I have been fixing the transducers directly across from each other as shown below.    

The image below shows my test pipe for zero flow measurements.  I have 1MHz transducers from Audiowell which have a 50 degree face and I place Magnalube-G as my couplant between the transducer and pipe.  A 2 piece 3D printed fixture is used to mount the transducers and held together with 2 hose clamps.  I am getting a good clean signal with this configuration using 22.8dB gain with the internal PGA.     

For metal pipes, you will likely need some external amplification on the receive side to get a proper signal and it is expected you will see more noise.  I still need to do more research on this, but I am experimenting with using the EVM430-FR6043 which includes external amplification on the receive side.  I will still need to change some of the filtering components and external amplification needs to be enabled in the software FR6043 demo software example.

From the wave form you show, you should first try to get a good signal at zero flow.  Again, you will probably need external amplification, but you could try without it.  Make sure your mechanical design is good and couplant is used and not dry.  You could try to reduce the gap between pulse start and ADC capture and increase the capture duration as it looks like you are not capturing the first part of the signal.  To reduce the gap without errors, you will probably need to increase the Start PPG count.  The thread below shows the relationship between the two.  This will give a better idea of what the signal looks like. 

http://e2e.ti.com/support/microcontrollers/msp430/f/166/p/761932/2817850#2817850 

Hi Eddie,

First of all thank you very much for your answer!

I have few questions about what you wrote?

1) Have you tested two-transducers-on-one-side configuration for clamp-on metering? What's the comparison between this approach, and the one you used?

2) Does FR6043 work with water metering? I thought it is only for gas applications?

3) How did you design the 3d printed thing? Do you happen to have design files? I would be most grateful for help in this matter. What are the guidelines when designing part like this?

I am looking forward to hearing back from you.

Best,.

Wojciech