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45 degree flow measurement inaccurate for TDC 1000 evm

Vinu Gopalakrishnan
Intellectual 635 points


Hi,

I tested the TDC 1000 - TDC 7200 EVM for flow metering application. I am using the Steminc 1Mhz transducer that came with the EVM kit. I modified the source code in such a way that it would run without any GUI support. The delta TOF that i obtained from the test is not satisfactory. The following are my issues.

1. A difference of time of flight of 5 to 6 nanoseconds for 3/4'' pvc pipe was obtained from the experiment. Whereas the actual flow rate was 960 litre/hour which gives a delta TOF of around 12 nanoseconds theoritically. 

2. Zero flow rate testing never gives zero delta TOF. Always an error of around 20 ns.

3. The delta TOF value is reducing when the water flows. I guess the delta TOF would increase upon water flow. This is totally against my expectation.

Note: I mounted the transducers using acrylic cylinders with glue in between. The setup gives accurate TOF values, but delta TOF is not correct .

Please help. 

regards,

Vinu

  • 0
    TI__Mastermind 21685 points
    Vinu,

    It sounds like you are constructing a flow meter transducer. We have used only off the shelf flow meter transducers and don't have experience in the construction of one as the flow meter standards demand very high accuracy. Please refer to this app note

    www.ti.com/.../snia020.pdf

    Appendix A has a list of flow meter transducer manufacturers and details (Section 5, Figure 4) of the Audiowell flow meter sensor pipe we have used.

    Also, please note we have only used "in flow" sensor where the transducers are in the medium (water) .


    Thanks,
    vishy