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BOOST-LDC3114EVM: Best sensor for high resolution inductance sensing

Ankush Dhawan
Prodigy 10 points
Part Number: BOOST-LDC3114EVM
Other Parts Discussed in Thread: LDC1612, LDC1312, LDC3114, LDC1614

Tool/software:

Hello, 

I am a researcher working on using an induction sensor to measure the 3-axis distance to pieces of metal foil. I have seen a few LDCs from TI, and I was wondering if anyone had any recommendations on which is suitable for my application.

Specifically, I am looking at which sensor would have the highest resolution. I have seen the sensors LDC1312, LDC1612, and this sensor LDC3114, and I was if someone could help me better understand what the drawbacks/benefits each of these have compared to each other, and which may have the highest resolution.

Thank you,
Ankush Dhawan

  • 0
    TI__Mastermind 40295 points

    Ankush,


    What is the most convenient and/or optimum resolution metric for your application?
    What metric(s) are you considering for resolution?

    These devices can be considered data converters with weird inputs, but traditional metrics used in conventional A/D converters don't readily apply.

    For example, we have a set of app notes that discuss resolution in terms of frequency:

    1. Optimizing L Measurement Resolution for the LDC161x and LDC1101
    2. Optimizing L Measurement Resolution for the LDC1312 and LDC1314

    The LDC161x devices have the widest output data registers (= 28 bits), but their highest sensor frequency is 10MHz.
    The LDC3114 output data registers provide a total of 24 bits per channel, but has a max sensor frequency of 30MHz.

    The LDC3114 is our newest inductive sensor, and its the only one with a Spice model, which may help work thru questions about system resolution.
    There is also an FAQ on how to use the model:  [FAQ] LDC3114: Pspice model, raw data mode

    The Spice model is mentioned only because the resolution is not completely determined by the output register width.
    The sensor frequency, sensor inductance range & shift due to a moving target, ambient noise, etc. all play a role in the overall resolution.

    Please let me know if you have any questions.

    Regards,
    John

  • 0 in reply to John Miller - Sensing
    Prodigy 10 points

    Hi John,

    Thank you for your note. My application specifically wants to determine minute differences in the movement of a metal foil via the eddy current effect, using one of these LDCs. For us, a frequency of 10 Hz is more than what we require. We will be doing testing in indoor room conditions, so the sensor shouldn't experience anything out of the ordinary.

    Going back to your note, would you say that then the LDC1614 or the LDC3114 would provide the finest differences in the milli-Henry inductance measurements of the coil? Also, does the number of bits per channel correlate with resolution (i.e. the LDC1614 has higher resolution). The inductance measurement range we are trying to work with are on the order of about 6-10 milli-Henry if that provides any more information.

    Ankush

  • 0 in reply to Ankush Dhawan
    TI__Mastermind 40295 points

    Ankush,

    Please take a look at our Inductive Sensing Design Calculator Tool.
    You can find it here.

    It allows you to design sensors and explore device settings or our LDC parts.
    You can also explore the sensor inductor/frequency shift over the range of target motion for the devices of interest.
    It can also help determine how much your design will exercise all of the available output dynamic range (e.g output resolution).

    The tool doesn't support all of the implementation details details, but it will give you a solid start.

    regards,
    John