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PGA460: PGA460-Q1

peter mccormick
Expert 1110 points
Part Number: PGA460
Other Parts Discussed in Thread: TDC7200,

We have experience with the PGA460 through air and it works very well.  Is there a way to use the PGA460 to measure water flow rates, similar to your TDC7200 for water flow meters?

Any APP notes to use the PGA460 with water flow?  Obviously, we would need to have a way of using the manifold and piezo crystals.  We like the PGA and have the software to run it so if we can use it on this additional product line, it would be great.

Thanks, Peter

  • 0
    TI__Mastermind 27950 points
    Hi Peter,

    We have not tried using the PGA460 for water flow applications, but if we assume that there exist a compatible transducer in the 30-480kHz range, you could use the PGA460's TCI interface to capture a real-time pin toggle. The IO pin is idle high when no object is present, and is pulled low while the echo data exceeds the threshold. The TCI interface can only be used in star topology (no bus), so you would need to synchronize the burst/listen command from multiple GPIO pins (at least two) for this type of implementation.

    The TCI communication mode is discussed in the datasheet. Though this interface was originally intended for automotive applications, it can be re-purposed for other real time capture systems. Note: TCI idles high at VPWR (6-28V). Let me know if you have any additional questions about TCI after reviewing the datasheet material.
  • 0 in reply to Akeem Whitehead
    Expert 1110 points

    Akeem, I think this might work.  How accurate is the PGA460, picoseconds or microseconds?

    Below is a simple diagram from your TDC documentation but it uses 2 PGA460.  We fire 1 PGA to measure time of flight downstream then the other PGA to measure upstream.  The inputs are tied to the other transducer.  The PGA reads the other transducer as shown attached.  This is much simpler than all of the TI TDC concepts as far as I can tell.  Maybe it is a crazy idea.

    Thanks, Peter

  • 0 in reply to peter mccormick
    TI__Mastermind 27950 points
    Hi Peter,

    The PGA460's ADC operates at 1MHz, so the finest available resolution is 8-bit sample output at 1us per sample. If you use the USART (SPI) mode, you can also get a 12 bit sample output at 2 us per sample. Alternatively, you can also capture the AFE output at the TEST pin for greater resolution, but you won't be able to utilize the benefits of the DSP.

    Your biggest challenge may be finding a compatible transducer for flow metering. If I recall correctly, the TDC typically uses a 1MHz for this type of application, while the PGA460 is limited to a maximum driver/receive frequency of 480kHz.
  • 0 in reply to Akeem Whitehead
    Expert 1110 points

    Another technology that we used years ago was Vortex Shedding Technology (VST).  We are considering it again here.

    en.wikipedia.org/.../Vortex_shedding

    Does TI make any products that perform VST?

    Thanks, Peter

  • 0 in reply to peter mccormick
    TI__Intellectual 1020 points
    Hi Peter,

    For high accuracy best in class water-flow metering applications, TI has a new MSP430 based solution. I would suggest that you check that out for your application: www.ti.com/.../overview.html

    You will find a lot of reference designs and documents using the new IC.

    Regards,

    Vaibhav Garg