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TDC1000-C2000EVM: Unable to get the EVM to generate start signal

Part Number: TDC1000-C2000EVM
Other Parts Discussed in Thread: TDC1000, TUSS4440, TUSS4470

Hello,

I am trying to use the TDC100-C2000EVM to measure tof in steel. I found that the tof I got didn't change with different lengths of steel. After probing the start buffer (TP23), I found that no signal was generated. All i saw was noise. Please I'd like to know if there's something I need to change in my setting. I have tried with two EVMs and different transducer frequencies but I still encounter the same problem.

My setup and response are attached.

Thank you very much

  • Hi Felix, 

    Sensing thickness of metal is unfortunately not realizable with the TDC1000. Due to the material characteristics of steel, the sound waves will be significantly attenuated upon entering the metallic object.

    It may be possible to utilize a high powered amplifier to excite a TX transducer and use the TDC1000 to sense the return echo, but even this would likely be difficult.

    You are welcome to alter the PGA gain to 21 dB, but I do not expect to see much of a difference in the TDC1000 output waveform.

    Regards,

    Jacob

  • Hi Jacob,

    Thank you very much for your response. I have tried the EVM on other types of transducers but there is no signal from the start buffer. I would expect that the transmission part is fine even if the echo is undetectable because of the attenuation.

    I would also appreciate if you could please suggest an alternative EVM for sensing thickness of metals.

     Kind Regards,

    Felix.

  • Hi Felix,

    You are correct, I would expect there to be a start pulse created even if the echo return did not qualify the threshold. 

    I am not certain there exists a single IC system that would realize a solution. 

    If you are willing to mount the transducer above the metal object, you could use the TOF measurement to calculate the thickness of the metal block.

    Do you have a range of material thickness you wish to measure?

    Additionally, is there an accuracy specification you require for the application?

    Please let me know if you have any questions.

    Regards,

    Jacob

  • Hi Jacob,

    Thank you very much. If the transducer was properly excited, I would have considered external amplifier for the echo signal for my application. Could it be that both EVMs are faulty?

    Yes I plan to mount the transducer on the metal object and the largest of the metal blocks is 200 mm on the wave path. I hope to achieve 0.4 ns TOF accuracy.

    I am considering the TUSS4470 (because of the possibility of using a 1 MHz transducer) or TUSS4440 (because of the transformer driver if I can't use TUSS4470). This is based upon what I found here: Ultrasonic Sensing ICs.

    Could you please advice if these are reasonable choices?

    Kind Regards,

    Felix.

  • Hi Felix,

    I'm not sure, what exactly could be the cause of not seeing a start pulse. The pulse width of the signal is only 1us wide, so it is necessary to use a trigger on the scope channel to accurately capture it. 

    It is possible the boards are not functioning as expected due to damage.

    I am not sure what will exactly be required to realize a solution that can sense up to 200mm steel. 

    I can say that the TUSS4470 is a better suited device than the TDC1000 for the application goals. This is because the TDC1000 is only capable of 41dB gain whereas the TUSS part can realize in excess of 110dB of receiver gain. 

    The best option in my opinion would be to use a bi-static configuration (1 transmit and 1 receive transducer) with the TUSS4470 and a suitable power amplifier to create a high powered ultrasonic burst. 

    It may be possible to realize a solution with a mono-static configuration, but I am guessing the attenuation of the steel will make the return echo unqualifiable. 

    Please let me know if you have any questions.

    Regards,

    Jacob

  • Hi Jacob,

    Thank you very much for your response. I will try the TUSS option.

    Kind regards,

    Felix.

  • Hi Felix, sounds great,

    Feel free to open a new thread if you have any questions on the TUSS4470 device.

    Thank you,

    Jacob