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Original question:

BOOSTXL-PGA460: Load a custom datapath to GUI

BOOSTXL-PGA460: Short range measurements

Jean Bouchat
Prodigy 130 points
Part Number: BOOSTXL-PGA460

Hello,

I try to reproduce the results obtained with the BOOSTXL-PGA460 modified for short range measurements (R38 10K and C15 680pF). But I can't achieve same performance.

With P1, I get  echo/resonance at about 130µs and get the following results with distance between 12cm ~60cm:

With P2, I get echo/resonance at 300µs and 950µs (first plot is without obstacle and second with distance varying from 12cm to ~60cm):

Do you have any idea where this "parasitic echo" comes from?

Best regards

  • 0
    TI__Mastermind 19610 points

    Hello Jean,

    Thank you for your questions and the data as well. Are the results shown here all taken from the BOOSTXL-PGA460 or is this on a custom board?

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    TI__Mastermind 19610 points

    Also, I forgot to ask if this was in a bi-static configuration or mono-static?

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 130 points

    Hello Isaac,

    These results are taken from the BoosxlpGA (with transformer) in mono-static config an with the murata MA58MF14-7N transducer.

    Regards,

    Jean

  • +1 in reply to Jean Bouchat
    TI__Mastermind 19610 points

    Hello Jean,

    Thanks for confirming the info. For a monostatic topology seeing an echo early on is typical behavior. The echoes that you are seeing at about 130µs, 300µs, and 950µs seem to be the transducer getting excited during transmission and slowly coming down afterwards, this is what is referred to as transducer ringing or decay. Since they share a transmission and return path this is the reason why you can see it on the echo data dump. Even though you did change the passive components it allows you to get closer measurements but does not completely get rid of the ringing. You might be able to get better performance if you decrease the number of pulses being transmitted as well as changing other settings.

    In this thread Akeem, recommended using the following: 

    •Set your Digital Gain SR Gain to x1. It is currently x2, which is why the echo data dump shows a saturated decay.

    •Set Preset 1 Burst Pulses =4 and Driver Current Limit = 100mA. For comparison, set Preset 2 Burst Pulses = 16 and Driver Current Limit = 400mA.

    •You may need to further reduce the AFE Gain Range to 32-64.

    •Tighten the Band-Pass Filter Bandwidth to 2 or 4 kHz.

    Increasing the transducers frequency also typically helps but this also begins to decrease your max detectable range. Normally, for a really close measurement like this it is recommended to use a bistatic topology in order to eliminate the transducers excitation and slow decay from your return path. This would allow you to essentially get near zero measurements. 

    If you have questions on how to set this up it can be done on the BOOSTXL-PGA460 I put some information on this response here: https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/1018076/pga460-decreasing-the-blind-range-of-detection-to-0-5-cm

    I hope this helps!

    Best,

    Isaac

  • 0 in reply to Isaac Lara
    Prodigy 130 points

    Hello,

    I made some additional measurements with SR=1, and band pass=2kHz.

    P1 is 4 pulses with 99mA and gain varying from 32.5 at startup to "mask" resonance, and then rising to 64.

    I made measurements at 12cm, 20cm, 30cm, 40cm and 50cm

    The measured values have a kind of offset between 4cm at 12cm distance (reported distance is 16cm)  and 2..3cm at 50cm (reported distance is 52.6cm). I don't know the exact origin of this offset since it is more than the pulses period, but I think it is not a big issue since it seems to be reproducible and and should be possible to calibrate the measurements.

    With P2 '(16 pulses at 400mA:), I get these results:

    The offset is bigger (19.4cm reported at 12 cm and 55cm at 50cm), but the signal is of course stronger

    In all cases, I think I will be able to get measurements with good calibration.

    Regards,

    Jean

  • 0 in reply to Jean Bouchat
    TI__Mastermind 19610 points

    Hey Jean,

    Thanks for the info. Glad to hear you are getting better and more consistent results!

    Make sure to use the info for results on the UMR and not from the echo data dump since it is just a down sampled representation of the actual data collected. The EDD is known to have a minor delay of a couple of centimeters, the UMR will have more exact measurements so make sure when you get to the calibration stage to use the UMR results to get closer results.

    Best,

    Isaac