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ldc10xx inductive sensors

Julian Worskett
Intellectual 255 points
Other Parts Discussed in Thread: LDC1041, LDC1051

I have three eval boards, LDC1000 1041 and 1051.

I am trying to detect a large metal object at a range of about 1 ft, so I have made a new coil about 7" in diameter. It resonates at 3 MHz with a 94pF parallel cap. When I run any device, I can see changes in the graph as I move the coil, but I want to optimise the sensor by changing eval board parameters.

When I try and change parameters on the GUI, it makes no difference to the performance at all. I suspect that the parameters are not been updated on the eval board.

Here's what I am doing:

 I change say Rp and the sensor freq, with the eval board connected but not streaming, on the red/green and white block icon, then hit read all. Then select the sine wave icon again, hit start, and I see the graph changing as I put my hand over the coil. However, the response is exactly as it was before changing parameters.

If my SRF of the inductor is 3 MHz, should I set the sensor freq to the nearest value of 3 MHz?

What am I doing wrong here, I am determined to make this work as the product is ideal for our application.

  • 0
    TI__Expert 6550 points

    Hello Julian,

    I am sorry you are having troubles with the GUI. I would need more information to assist. Are you trying to detect the presence of the metal or the composition of it? What I am trying to get from here, are you using L and Rp measurements or L measurement only?

    You should set the sensor frequency to a lower frequency than Fsensor. Thus, you will ignore any lower frequencies and get better noise performance.

    If you could post a screenshot of the data, it will be helpful.

    Best Regards,

    Natallia Holubeva

  • 0 in reply to Natallia Holubeva1
    Intellectual 255 points

    Thanks Natallia,

    I am trying to detect the presence of the metal only, which will be steel, in fact I am trying to make a ground sensor to detect vehicles passing over it..

    I am confused as to what information can be obtained from Rp and the inductance, I understand inductance reduces in the presence of metal and that Rp goes down as the Q of the coil reduces (I am an RF engineer by trade). Is there a paper that describes this, I have not been able to find anything.

    I think my problem is with the GUI, in understanding when data is transferrred to the board.

    I never see any data or movement on the right hand graph, so inductance and count value are not live.

    Also, I am unsure about the practical differences of the LDC1000, 1041and 1051, under what circumstances would you use each model?

  • 0 in reply to Julian Worskett
    TI__Expert 6550 points

    Hello Julian,

    The L measurement is being used when you want to sense the presence of the target. The Rp measurement is being used when you want to sense the composition of the target or the presence in some cases (for example, ferromagnetic properties of the target have a blanc spot for inductance change). Unfortunately, there is no specific documentation I can refer you at the moment, but we are working on it.

    LDC1051 is for Rp measurement only, and LDC1041 has 8 bit Rp and 24 bit L resolution. So the difference is mostly in the resolution you need for your system.

    I see your inductance measurement is not functionning correctly. If you are using LDC1051, this feature is not availble by default.  Otherwise, you should get a reading. Please, make sure you oscillator is working properly. Also, you could try reinstalling or upgrating the GUI and the firmware on the EVMs (SW is available on our website).

    Best Regards,

    Natallia Holubeva