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MSP430FR6047: CCS/MSP430FR6047 how to measure Q flow according to the flow measuring tube in EVM430-FR6047.

Part Number: MSP430FR6047
Other Parts Discussed in Thread: EVM430-FR6047


Our company is trying to develop a water meter using the MSP430FR6047.

So, I would like to know how to measure Q flow according to the flow measuring tube in EVM430-FR6047.

We are creating a test environment with AudioWell's DN15(HS0014) and DN20(HS0016).

However, I have a question, so I would like to contact you.
In general, it is known that water meters have different Q1 (minimum flow rate), Q2 (transition flow rate), Q3 (maximum flow rate), and Q4 (overload flow rate) for each measuring pipe.
Are the Q1/Q2/Q3/Q4 mentioned above values that can be obtained through calibration?
Or is there an explicitly set value?
To check Q1 and Q3, which test and what value should I check?

Also, how do you calculate the maximum allowable error?

This is my first time developing a water meter, so please explain in detail.

thank you

  • Hi JunChul,

    Q1, Q2, and Q3 are all values that you can obtain through calibration of the device in the hardware set-up. In our device datasheet, we specify a rough minimum flow rate of <1 liter per hour. In our FAQ for USS Flow Metering Devices we note that we can monitor flow rates of up to 8800 liters per hour in a DN25 pipe, and customers have tested flow rates above 29000 liters per hour using a DN45 pipe. The range of achievable flow rates is so broad because it largely depends on the hardware set-up and environment. In other words, there is not an explicitly set value. Low noise environments and high quality transducers which make good contact with the pipe (or are mounted through the pipe so they directly contact the water) can allow for better signal strength, and therefor a better flow metering range.

    I think that a good starting point would be to go through the MSP430 USS Academy which will walk you through the basic use, and features of the MSP430FR6047. It also shows you how to characterize the errors in measurements. For an accurate determination of error, we recommend that you test your calibration using a mechanical meter so you can compare the flow rates and pinpoint your calibration. The maximum allowable error is up to you to determine. Once you have determine the error that is acceptable in your application, you can work on fine-tuning your calibration and hardware in order to fit your maximum allowable error.

    If you are expecting to measure a flow that varies across a large range, you should also take a look at the Flow VFR Calibration section of the USS design center users guide. I'd suggest that you look at this after using the academy.

  • Thank you for your reply.

    I understood that the exact values of Q1 and Q3 can be obtained through device calibration.

    In the "FAQ for USS Flow Metering Devices" document, section 1.2.11, we see that testing is required at multiple flow rates.

    So, can I understand that when configuring a test environment for calibration, we need to configure an environment that takes Q1 and Q3 into consideration?

    Also, in the case of existing water meters that can be used as references, the values are Q1 and Q3. I am curious as to whether existing water meters that are larger than the Q1 and Q3 ranges of the water meter to be developed should be used as references.

    Also, when configuring the test environment, a water pump is used, which produces a lot of noise and vibration, so a lot of noise is mixed in during the measurement.
    When configuring the calibration test environment, is it necessary to create an environment without any noise or vibration? Also, I am curious whether the calibration test will be affected by laptop or general household noise or vibration.

    Please give me advice on how to configure the calibration test environment.

  • I have an additional question about the project.

    I confirmed the following phrase from Slau810b-Water-Flow-Meter-Quick-Start-Guide.pdf.

    And, in the FAQ, there is the following phrase:

    Is it correct to check Q1(minimum flow rate) in the Zero Flow Drift Test?

    When checking Q1 (minimum flow rate) in ZFD, I used the GUI default of 12742000.00 as the meter constant. Is there any problem?

    In the case of zero flow (ZFD), the existing meter that serves as a reference only displays 0, so M2 = M1x(Y/X), which is the meter constant, cannot be calculated.


    When testing with AudioWell HS0014(DN15) for 15 minutes, the results below were obtained.


    (In the case of ADC Capture, the gain was set as low as possible, down to -6.5 db.)

    Captures are taken once after 5 minutes, and 3 captures for 15 minutes are as follows.


    If it is correct to measure Q1 (minimum flow rate L/H) in zero flow (ZFD),
    Can we assume that the Mean value in the picture below is Q1?

    Or should Q1 be 0.056 L/H, calculated by multiplying the last volume value by 0.014L, which is a 15-minute measurement, by 4?

    Additionally, the maximum tolerance (accuracy requirements) are listed below in the FAC document.(yellow marking)

    If the accuracy requirement is +/- 5% in square meters (m3) per hour, is +/- 50L/H the allowable range?
    Or is there a separate way to calculate whether the accuracy requirement is +/- 5% in the 15-minute measurement graph?

    Please help


  • When you say "an environment that takes Q1 and Q3 into consideration", what do you mean by that? When you are configuring a test environment, you should be aware of the Q1 and Q3 that you'd like to achieve and design the test in a way that allows you to reach your desired values. for example, the pipe size and material, transducers and mounting technique, etc. Please elaborate so I can help you answer this.

    For the reference meter, yes you should choose a reference meter that is accurate at the Q1 and Q3 values that you want. This may entail getting a reference meter that has a Q1 and Q3 range beyond the needs of the device you are developing, just to be sure you can get accurate test data.

    As for the pump noise: You should certainly work to mitigate noise during your calibration, as noise will affect your readings. However, it is unrealistic to create a zero-noise environment, or something that close to it. You should try to block noise from the pump, and shield the device from it, but you don't need to make some complex zero-noise environment for the calibration. The device was designed under the assumption that there would be some noise.

  • The Zero Flow Drift test is intended to show the drift/accuracy of the transducers and calibration set-up, not the Q1 of the device. I see in your ZFD test, you are seeing an average dToF of around 10-15ps. This is quite good. Once you have tested this across a number of transducer pairs, and have established a statistically reliable average dToF during ZFD, you can now use this value in your calibration settings under Configuration-> Advanced Parameters-> Deltat TOF Offset. This value will allow you to center your dToF around 0ps, giving you more accurate flow measurements.

    For the meter constant, it is ok to use the default for ZFD testing, as this just checks the dToF. However, once you start testing various flow rates, you will need to adjust the meter constant yourself so that the volume flow rate calculated by the MSP is accurate to the actual water volume flowing through the pipe. This is where the reference meter is very helpful.

    Your ADC capture also looks good. The amplitude is slightly high but I see you are already using the lowest available gain. However I think that the amplitude is fine and you should not have any issues.

    You should not assume that the mean value reported in the ZFD test is your Q1, nor should you use it to determine your Q1. You will determine your Q1 by setting the calibration, and then checking the volume flow rate error at various flows. It is also up to you to determine the allowable error for your Q1, so this is entirely up to you. If you determine that you want to set the maximum error at 5%, then you can calibrate the device, then use the reference meter to check the error. Reduce the flow rate until you see a 5% error, and that is your Q1. The USS GUI does not directly report your Q1.

    As for your question about the error tolerance, +/-5% error would mean different water volumes at different volume flow rates. If your volume flow rate is 100 liters per hour, and your error tolerance is +/-5%, then the volume flow rate range including error would be 95-105 liters per hour, or 100 +/-5 liters per hour. I could not say what the allowable range is for you, as I do not know your accuracy requirements, nor do I know the volume flow rate that you are testing the accuracy for.

    Please let me know if you need additional clarification on these.

  • Thans for reply!

    After confirming Q1, Q3 and the maximum allowable error, Q2 and Q4 are calculated to derive the results.

    error tolerance

    expected 15 mm













    For HS0014 (DN15) through testing in no-flow
    When setting the DToF offset to -12ps, the same results as the 15-minute measurement graph were obtained.

    At this time, the last VFR value is measured as the value closest to 0.

    If it is lower, the VFR mean value drops to -value.

    Is it correct to set the DToF offset in ZFD and perform calibration based on that standard?

    I wonder if there are any additional tests that need to be performed in ZFD testing.

    Also, in the case of flow testing, can we only conduct tests at Q1, Q2, Q3, and Q4 flow rates?

    I have additional questions.
    I lowered the DToF offset to -12ps and got the same result as the graph. Where can I apply this to the source code?


  • It is correct to set the DTOF offset as you have done during the ZFD test. 

    Additional tests for after ZFD testing are described in the MSP430 USS Academy, which I have linked above. The only other thing that I look at during ZFD testing is the ADC capture to make sure it looks good. You can compare your captures to those shown in the academy to determine if yours are good. However, looking at your DToF and AToF, I get the impression that your ADC captures are good, because those values are calculated using the ADC capture.

    You can conduct flow testing at any rate that you like, just be aware that your calibration and meter constant are optimized for a particular flow rate, so the error that you see may be a little larger at some flow rates. If you'd like to look into setting multiple configurations for multiple flow rates, you should look into the VFR Calibration section of our software guide as I mentioned in my previous responses. This will be helpful if you plan to measure flows across a broad range.

    If you'd like to apply the DToF offset directly in the code, instead of through the GUI, you can do so by setting the value of USS_ALG_DCOFFSET. If you take a look at the USS Design Center Users Guide, you can find a list of all of the GUI parameters and their corresponding values in the source code.

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