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EVM430-FR6043: Clarification on acousticLength and reference temperature in USS Gas Demo (EVM430-FR6043)

Igor Man
Prodigy 50 points

Part Number: EVM430-FR6043

Hello,

I'm working with the EVM430-FR6043 and using the USS Gas Demo firmware. I have a question regarding the correct configuration of the transducer spacing.

From what I understand, instead of specifying the physical distance L between transducers, the firmware expects the user to set the acousticLength parameter — which represents the time of flight (TOF) at a known reference temperature.

I found the following in the documentation:

> acousticLength  
> float _USS_Meter_Configuration_::acousticLength  
> Acoustic length in usec at room temperature.

However, the documentation does not define what "room temperature" actually means — whether it's 25 °C, 20 °C, or something else.

Could you please clarify:

1. Is it correct that acousticLength replaces the need to specify the physical distance L?
2. What exact temperature is assumed for "room temperature" in this context?
3. Does the USS library assume a fixed reference temperature internally, or is there a way to specify the temperature at which acousticLength was calculated?
4. How critical is this reference temperature for accurate flow measurement in gases? Since speed of sound in gas is highly temperature-dependent, I want to avoid systematic errors.

I’m trying to ensure that my configuration is physically consistent and that the flow calculations are accurate.

Thanks in advance for your help!

Best regards,  
Igor

  • 0
    TI__Mastermind 30406 points

    Hi Igor,

    See my comments as below:

    1. Is it correct that acousticLength replaces the need to specify the physical distance L?

    -> the distance means fly length for ultrasonic.


    2. What exact temperature is assumed for "room temperature" in this context?

    -> 25C


    3. Does the USS library assume a fixed reference temperature internally, or is there a way to specify the temperature at which acousticLength was calculated?

    -> actually our USS library just calculate AbsTOF and dTOF, thus this not rely on temperature.. Temp will have some impact for ultrasonic speed maybe, thus will need some calibration based on different temp point. But this should happen on final flow rate phase. We just provide AbsTOF and dTOF.

    Of course, we had some simple demo to calculate flow rate based on AbsTOF and dTOF, but this not very accuracy, just show function, because user will nee more calibration based on their actual use case.  


    4. How critical is this reference temperature for accurate flow measurement in gases? Since speed of sound in gas is highly temperature-dependent, I want to avoid systematic errors.

    -> this will depend on transducer performance in different temp, we just check ADC waveform, need ensure good ADC waveform, then you will be able to get good result.

    Thanks!

    Best Regards

    Johnson

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