MSP430FR6047: Abnormal water measurements.

Hi Nomikos,

Is this measurement taken with an off-the-shelf pipe (like AudioWell)? Or custom?

If custom, can you tell me more about the design and who is the transducer manufacturer and what is the rated frequency?  I assume 1MHz based on your settings, but just wanted to double-check.

Hello Denis,

The tranducers used have a rated frequency of 1MHz and are manufacted by Zhejiang Jiakang Electronics and the pipe is not custom made. The pipe is DN15. I will try to record more accurate ADC graphs from our design to better understand the issue. 

Hello,

I was able to capture better graphs using the GUI with our MSP on the pcb. The distance of the transducers is 56mm. Yes the frequency sweep reaches a peak at 1000 amptitude and then starts to decline. 
While searching I found an answer to a similar issue form user Cash Hao11 that states that the issue seems to be Cycle Slips. Could you please elaborate on the issue. 

There are some graphs when the issue appears.

Here I changed the ADC Gap and the issue appeared.

Frequency 1000

Gap 40 

Pulses 25 

Threeshold 28

Hello,

Would you require more information from us about the issue?

Nomikos Panagiotis

Hi Nomikos,

Please refer to this training.

From the training material:

Repeatability Analysis

At high flow rates, there may be variations in the amplitude of the downstream received signal. This can cause significant variations in the absolute Time of Flight measurements. Because the absolute Time of Flight measurements are used to determine which correlation peak to lock onto for the delta Time of Flight measurement, variations in the absolute Time of Flight greater than half a cycle can cause cycle slips in the measurement results.

Cycle slips might also occur at higher flow rates at -25C due to changes in the ADC capture which cause the absolute time of flight measurement to shift by more than half a cycle. Using more dampened lower frequency transducers or modifying the tube design to reduce the velocity of the flow in the tube can resolve these problems. If the shift in absolute time of flight is due to continued excitation of the transducer at these colder temperatures, the F2 transmit frequency can also be increased to more quickly dampen the excitation.

Hi Dennis,

Thank you for your response. Just wanted to point out we are developing a water meter and the information provided were about gas metering. I forgot to specify it before. We will perform ADC captures and see how they behave in higher flow rates. One more question I would like to make is that after the issue appears even if we return the flow to zero and the ADC is normal the issue still appears and it could remain in that state for days. Shouldn't we excpect normal readings then.

Thank you for your time

Nomikos Panagiotis