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LDC1612EVM: To use the LDC1612EVM evaluation board for non-invasive and contactless liquid conductivity monitoring

Yashwanth Ramesh
Prodigy 20 points
Part Number: LDC1612EVM
Other Parts Discussed in Thread: LDCCOILEVM, FDC1004

Tool/software:

My name is Yash, and I am a graduate student working on liquid conductivity measurements. I am currently using the LDC1612EVM evaluation board, which comes with coils connected to each of the two channels. To experiment with different inductance values and Q-factors, I also purchased the LDCCOILEVM evaluation board for testing alternative coil configurations relevant to my application.

In my experimental setup, I poured a salt solution into a glass container and situated the coil on the outer wall of the container. The coil was connected to the evaluation board, which was then connected with my computer and I tracked my measurements via the TI GUI for inductive/capacitive sensing. Now, when I increased the conductivity of the solution inside the container, the GUI consistently showed that the inductance of the coil increased as well.

I would like clarification on the following points:

  1. Cause: What possible physical mechanism causes the inductance to increase with increasing solution conductivity?

  2. Correctness: Is this response expected, or could it be an artifact / error of the measurement system?

  3. Application: Can this method serve as a reliable, non-invasive, contactless approach for liquid conductivity measurements?

Note: For experimental consistency, I ensured that the liquid volume inside the container remains constant across all conductivity levels.

Thank you for your time and guidance.

Best regards,
Yash

  • 0
    TI__Prodigy 200 points

    Hello Yash,

    1. As the conductivity of your target increases, the inductance will increase as well.
    2. This should be repeatable but more testing may be needed. Try changing the amount of salt in the solution by a fixed amount and remeasuring the inductance. With some number of measurements you should be able to determine if there is a trend.
    3. To determine if this is valid method, you need to determine the noise floor of your system. You can find this by testing the system with no liquid (target). You would then take the standard deviation of the data collected and compare that value to the change in the output data when the liquid is present.

    Typically capacitive sensors (such as the FDC1004) are used for liquid level sensing, please refer to the app note here.

    I hope I was able to assist you with your problems. If you require any further assistance, please reply below.

    Thank you,

    Chase Girard