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LDC_COIL_EVM

HIROAKI YOSHIDA
Intellectual 290 points
Other Parts Discussed in Thread: LDC0851, LDC0851EVM

Thank you very much for your help.

Please let me know about LDC_COIL_EVM.

1. About sensor capacitors
Overview of the LDC Reference coils user's guide states that
Overview of the LDC Reference coils user's guide, it is stated that "Sensor capacitors are not included by default, so you will need to solder in appropriate sensor capacitors.
Is this also the case when connecting to the LDC0851_EVM with a 68PF capacitor mounted?

I actually connected the H coil of LDC_COIL_EVM to LDC0851EVM, but the sensing operation resulted in discontinuity.

2．Questions about the sensing operation
I conducted a sensing experiment by gradually increasing the distance between the sensor coil surface and a metal object, but the output from the LDC0851EVM does not turn ON at a specific detection distance.

For example, the output of LDC0851EVM turns ON when the end of the sensor coil is +16mm~+27mm.
For example, the output of LDC0851EVM turns ON when the sensor coil end is +16mm~+27mm, and the output of LDC0851EVM turns OFF when the sensor coil end is +27mm~+32mm.
The output of the LDC0851EVM turns ON for the sensor coil end +33mm~46mm.

The above is all I have to say.

  • 0
    TI__Mastermind 18535 points

    Hello, 

    If using with the LDC0851EVM, the capacitor for the LC tank is already on the LDC0851EVM and you do not need to populate the coil EVM. 

    I have a couple questions for you on this issue:

    • What setting for the ADJ are you using? 
    • Can you take an oscilloscope capture of the sensor and reference coils for these cases? 
      • What is the frequency of oscillation? 

    Thank you, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Intellectual 290 points

    Justin Beigel

    Ich möchte Sie über die Diskontinuität im Erfassungsverhalten beim Anschluss des LDC0851EVM an die H-Spule des LDC_COIL_EVM informieren.

    -1.Experiment with LDC0851EVM and LDC_coilEVM

    -2. ADJ
    　Wenn ADJ auf einen bestimmten Wert eingestellt ist, wird der Abtastvorgang nicht unterbrochen; er erfolgt bei jeder Einstellung von MIN bis MAX.

    -3. Oszilloskop-Wellenform

    Die folgende Tabelle zeigt die LREF-Wellenform auf der Seite der Referenzspule, die LSENSE-Wellenform auf der Seite der Sensorspule, die
    　Oszillationsfrequenz und den Ausgangsstatus des LDC0851EVM.

    ①At the coil end, when the output of LDC0851_EVM is OFF

    　Oscillation frequency・・・1.29MHz

    【LREF　SIGNAL】

    【LSENSE　SIGNAL】

    ②The coil is near the center: the output LED of LDC0851EVM is blinking

    　Oscillation frequency・・・1.34~1.38MHz

    【LREF　SIGNAL】

    ③The coil is near the center and the output LED of LDC0851EVM is almost on.

    　Oscillation frequency・・・1.95~2.13MHz

    【LSENSE　SIGNAL】

    ④Operation of the problem beyond the coil_center position

    　Oscillation frequency・・・3.19~3.27MHz

    The above measurement waveforms are attached.

    I would like to understand what causes the discontinuity in sensing operation, so please let me know.

  • 0 in reply to HIROAKI YOSHIDA
    TI__Mastermind 18535 points

    Hello, 

    I have a couple questions about your setup:

    Are there 2 blue cables in your setup or is the GND connected to the COM pin? 

    What is the distance between the metal plate and the sensor coil? 

    Can you test without the second set of coils next to the ones you are using? They are very close together and are a concern for coupling as the target covers more of the sensor coil. This may be what is causing the discontinuity in your sensor coil. 

    Best Regards, 

    Justin Beigel

  • 0 in reply to Justin Beigel
    Intellectual 290 points

    Mr. Justin Beigel

    Thank you for your help. Thank you very much for your answer.

    1. The two blue cables
    One of the two blue cables you mentioned connects the LDC0851EVM to the ground of the oscilloscope. The coil is the LSENSE signal.
    Should the GND be connected to the COM pin?

    2. distance between the metal plate and the sensor coil

    I tried the distance from 0 to the limit of the LDC0851EVM detection distance.
    When the ADJ volume was set to the minimum to maximum, the distance was 7.9mm, but this sensing
    If there are discontinuities in the sensing behavior, is the LDC0851EVM's judgment correct?

    3.About the adjacent coil

    The adjacent coil is the I coil of the 4-layer board, but in the case of the I coil, the sensing operation is
    In the case of I-coils, the sensing operation does not seem to be discontinuous.

    After the sensing experiment of the I coil, should I remove the I coil and conduct the sensing experiment of the H coil again?

    Please let me know what you think.

  • 0 in reply to Justin Beigel
    Intellectual 290 points

    Did you receive the inquiry I sent you earlier?
    I have not received a response email, so I wanted to check.

  • 0 in reply to HIROAKI YOSHIDA
    Intellectual 290 points

    Mr. Justin Beigel

    Thank you for your help. Thank you very much for your answer.

    1. The two blue cables
    One of the two blue cables you mentioned connects the LDC0851EVM to the ground of the oscilloscope. The coil is the LSENSE signal.
    Should the GND be connected to the COM pin?

    2. distance between the metal plate and the sensor coil

    I tried the distance from 0 to the limit of the LDC0851EVM detection distance.
    When the ADJ volume was set to the minimum to maximum, the distance was 7.9mm, but this sensing
    If there are discontinuities in the sensing behavior, is the LDC0851EVM's judgment correct?

    3.About the adjacent coil

    The adjacent coil is the I coil of the 4-layer board, but in the case of the I coil, the sensing operation is
    In the case of I-coils, the sensing operation does not seem to be discontinuous.

    After the sensing experiment of the I coil, should I remove the I coil and conduct the sensing experiment of the H coil again?

    Please let me know what you think.

  • +1 in reply to HIROAKI YOSHIDA
    TI__Mastermind 18535 points

    Hello, 

    Thanks for clarifying the blue cables.

    HIROAKI YOSHIDA said:
    Should the GND be connected to the COM pin?

    No, the GND and COM should not be connected. 

    7.9mm should be fine for this coil size. I don't think you will have to change this. 

    HIROAKI YOSHIDA said:
    After the sensing experiment of the I coil, should I remove the I coil and conduct the sensing experiment of the H coil again?

    Yes, when you are done with coil I, you should test H again without the I coil nearby. Even though coil I is not having issues, it's presence may be impacting coil H. 

    Best Regards, 

    Justin Beigel