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PGA460: Transducer disconnect diagnostics

user6060721
Expert 1015 points
Part Number: PGA460

https://e2e.ti.com/support/sensors/f/sensors-forum/942124/pga460-pga460-detect-transducer-disconnect/3486306?tisearch=e2e-sitesearch&keymatch=%252525252525252520user%25252525252525253A432771#3486306

This post talk about Transducer disconnect diagnostics.

I think only monostatic mode can do diagnostics,bi-static mode can not.

Is this right?

I use bi-static mode, i do diagnostics when there is no object in front of transducer,the result is wrong.

So when use bi-static mode,we can not do diagnostics if no obstacle.

  • 0
    TI__Mastermind 21170 points

    Thank you for reaching out with your question.  There are four main diagnostic functions for PGA460:

    1. Excitation Voltage
    2. Transducer Frequency
    3. Ring Decay Time
    4. Noise Floor

    Which of these are you observing an incorrect response? Could you provide more details regarding the difference you see with and without a target?

    For diagnostic items number 1-3, these are run during a normal burst period as shown here with the corresponding numbers shown on the plot.

    These tests should not be dependent upon the target presence.  During the burst and decay periods, the Tx transducer should behave the same regardless of any echo which would typically be small in comparison to the output burst. What range is the target when the diagnostic runs correctly?

    The noise diagnostic occurs in a listen only mode where no burst should be present.  

    Thanks,

    Scott

  • 0 in reply to Scott Bryson
    TI__Prodigy 300 points

    Hi Scott,

    Please let me on behalf of my customer user6060721.

    I think the key point of this question is bi-static mode. As my understanding, all the diagnostic items number 1-3 are rely on connection between transmit probe and INP/INN, which is the typical application of mono-static mode.

    But in our customer's application, INP/N are only connect to the dedicated receiver probe. In idle condition, there is no signal can be detected during the burst.

    By this way, how to diagnostic the transducer (transmit probe or receiver probe) disconnect?

    Thanks.

  • 0 in reply to Shawn Liu
    TI__Mastermind 21170 points

    I have investigated this point further and have found that the diagnostics are exclusive to monostatic mode.  

    This does make disconnect detection more difficult. One possible work around would be to add integrated analog switches/multiplexors in the system temporarily swap the device setup to monostatic for this purpose, but my concern with this option is that it adds a fail point to the system. 

    Depending on the transducer behavior, it might still be possible to determine a disconnect if the ambient noise level is significantly different during a disconnect on the receiver.\

    Otherwise, detecting a disconnect would likely require having a known condition with an expected echo to test the full loop for an expected response.

    Thanks,

    Scott

  • 0 in reply to Scott Bryson
    TI__Prodigy 300 points

    Hi Scott,

    Got it. Thanks for your quick reply.