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MSP430FR6047: Atypical values on flow rate calculation for Water Flow Meter Application

Part Number: MSP430FR6047

Hi experts,

I´ve been working on a flow meter application, but I´m having some troubles with de Flow Rate calculation (non calibrated).

I´m working on mili-liters per second. The issue is that, when working on flow rates below 500 ml/s, it works all fine. But when I increase the reference flow up to 600 ml/s, I get some alteration in the flow, going from a real and reasonable measurement to an abnormal flow rate, as seen in the picture.

I´m using the following configurations. I'm using only, for now, the non calibrated value.8666.USS_meterVFRCalibFlowTemperature.h  2480.USS_intrplCorrLUT.h 6114.USS_temperatureLUT.h

I would really appreciate your help.

The picture shows the common values around 650 ml/s, but we get some values up to 3000 ml/s. We have also notice, using the USS GUI, that this values show when UPS increment its value, but DNS keeps a normal value.

  • Hi,

    How much does the UPS absTOF increase in this situation? Assume you are using 1MHz transducer, then one cycle of the receive signal is 1us. Does your UPS absTOF value change around 1us which is 1 cycle? 

    If so, we called this phenomenon as cycle slips. It mostly likely caused by inappropriate configuration, like envelope crossing threshold.  It would be helpful if you can share a screen snip of the ADC capture data and the configuration here to solve your issue. Or you can follow this academy on how to get a proper configuration on your meter.

    Best regards,

    Cash Hao

  • Thank you for your fast answer.

    We´ve increased the gain to maximum value, and we got rid of this issue in ambient temperature (20-25°C), but when getting on temperatures of around 40°C we found the same behaviour in flow rates around 400 ml/s.

    Is it an experimental balance between gain and envelope crossing threshold?

    Best regards!

  • Hi,

    Could you share a screen snip of your ADC capture data and the configuration page as well under room temperature and at 40 degC.

    The point to set the envelope crossing threshold is to find a stable lobe which has a stable proportional to peak lobe and significantly different from the adjacent lobes under all temperatures. 

    Best regards,

    Cash Hao 

  • Thank you so much for your answer. I'm sorry for the delay. We've been solving some issues with the ADC signal first, then we started modifying some issues with our meter physical design so we are about to test new results.

    As fast as we finish testing, I´ll post the results.

    Thank you so much for you attention.

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