MSP430FR6047: High flow rates even at zero flow

Hi Panagiotis,

Could you share the ADC waveform?

Thanks!

Best Regards

Johnson

Hi Johnson,

Because this is a custom board from us I will have to create the graph manually and it might take me some time. When I have it i will send it. i believe my issue is the same as the one with the question linked. I have followed the suggestions there and the only thing left to check is the Envelope Crossing Threshold.

Thank you for time!

Best Regards

Panagiotis 

Hi Panagiotis,

Understood.

Thanks!

Best Regards

Johnson

Hi Johnson,

I used the evaluation board that I have to take some measurements and make adjustments. I will attach the ADC waveforms and the configuration used. What I found is that I had set the Gap between pulse start and ADC capture too high, at 55, and by calculating it from this: ADC Start Capture Time = (Ultrasonic Path Length/Speed of Sound) – 10us the new gap turned to 27. This alone demostrated huge improvment on the issue as many of the affected meters were measuring correctly. But the issue does appear again in other boards or even in boards with new configuration although less frequently. 

Best Regards,

Panagiotis

Hi Panagiotis,

You can increase a little for ADC Start Capture Time, maybe 30, maybe 35. 

The you can get the waveform in the center, this will be better to get more accuracy value.

Thanks!

Best Regards

Johnson

Hello Johnson,

This is the ADC with 30:

Does this look better? Is my Envelope Crossing Thresshold set properly? Is the issue I face derive from this wrong set up? 

Thank you for your time

Nomikos Panagiotis

Hi Panagiotis,

You need optimizate the below items to fix your issue:

• Change this para(ADC Start Capture Time) to move this wave into center of duration.
• Add the number of Pulse
• Increase the Gain to let the waveform work in about 1000 value

Thanks!

Best Regards

Johnson