EVM430-FR6047: Clamp on Transducer with 2 inch pvc pipes configuration settings.

Hi Darshveer,

To be clear, this set up is for zero flow?

Your ADC capture looks mostly good but please try to increase your gain so that the amplitude reaches 800-900 units.

It looks like the default envelope crossing threshold is 11. Did you increase yours to 25 because it gave you better results? 25 is not necessarily wrong, I am just wondering if you've tried experimenting with this setting. 

You may want to try reducing the number of pulses to see if this helps.

The only other thing that I noticed is that in the image of your hardware setup, the transducers are not quite in line with each other. If you slide them so that they do point directly at each other, this may help.

Ultimately, your set up looks quite good and I am surprised you are having these issues. If you make these small adjustments and are unable to get closer please let me know and we will continue to look further into this.

Hey Dylan,

We are having flow through the test setup so that should not be an issue.  I have changed the envelope crossing threshold back to 11 and am getting a better ADC capture within the range you have given.

I also attempted to reduce the number of pulses and found that the best value was 24 as shown in the images attached. As you can see from the waveforms the given value for gallons per minute is still very erratic and not sitting close to the 12 GPM that our mechanical flow meter is indicating. 

If we try to align the transducers more the ADC capture starts to get worse, for this reason the transducers appear as they are in the picture. 

Please advice on the next course of action,

Thank You

Darshveer,

You should perform zero-flow testing, and use this to adjust your calibration for the device, before conducting testing with flow through the test environment. 

I am glad you were able to get a better result with the adjusted envelope crossing threshold.

If you have optimized your transducer set up, and found that this configuration works best, then we can leave it alone. 

I am unable to see the images you posted as you used an external link. Please just upload the images to this site using the insert tab in the text box. I am still wondering if the high number of pulses is leading to an issue. In the first image that you posted, the adc capture shows a waveform with an envelope with multiple peaks. This leads me to believe that the device is not correctly determining where the right peak is, and is using different peaks in each calculation of flow, causing the erratic measurements that you are seeing.

I am using similar settings to yours, the difference in the ADC capture is that my envelope has only one peak (likely due to less reflection, ringing, interference, etc) and I am getting good readings. 

As a final check, have you checked that the absolute time of flight is as expected? You can calculate the expected time of flight by dividing the distance between the transducers by the speed of sound in water. Adding a flow will change this but for zero flow the device should read a similar value to your calculations. If the values are off then your device is probably reading ringing or something else.