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TDC1000-C2000EVM: ToF Value from the TDC1000-C2000EVM Remains Constant

SEMYALO DENNIS
Prodigy 30 points
Part Number: TDC1000-C2000EVM
Other Parts Discussed in Thread: TDC1000

Tool/software:

We intend to use the TDC1000-C2000 EVM board for measuring water levels with the H4P10B1000 PZT4 1MHz transducer. Our initial configurations involve using the TDC1000 GUI tool.

Initially, we wanted to test if the sensor could measure the width of a water-filled container, so we attached it to the side of the container, as shown in the photo. The dimensions of the container are 28.5 x 18.5 x 15.5 cm (L x W x H). Using the attached configurations, achieved after several adjustments, we obtained a ToF of about 253 μs for this width, which corresponds to approximately 18.7 cm using the formula provided in the user guide.

However, when we change the position of the sensor (either to lengths shorter or longer than 18.5 cm), the ToF remains unchanged. For instance, we placed the sensor at the bottom of the container where the water level was about 6 cm, so we expected the sensor to show a ToF value corresponding to that level.

Why does this value remain constant, and what do we need to change to ensure the ToF values correspond to the actual level (distance being measured)?

Thank you in advance.

  • 0
    TI__Mastermind 21410 points

    Hello Dennis,

    Thanks for posting to the sensors forum! Thanks for the information, it seems like one of your colleagues made a post as well the thread can be found here, but I will be responding to all the questions through this thread.

    I see that there are two transducers on the plastic tank one of them looks like it has just been taped on there and the other one perhaps glued on there. Did you follow our guide on how to mount transducers? Here is the document if needed:  https://www.ti.com/lit/an/snaa266a/snaa266a.pdf

    This could be the issue for the stable time of flight, but another common issue is that the timing registers have not been configured properly, so the listening window is sometimes activated too early. Have you reviewed this configuration to see if the device is listening for the echo at the appropriate time?

    The figure below shows all the settings that configure the listening window for the standard ToF setting: 

    One last thought is that sometimes the tank could also be an issue. If there is an airgap inside the tank meaning there is a wall | air | wall  this could be an issue as a lot of the SPL is lost or returned when the medium changes.

    Best,

    Isaac