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LDC1000 to measure liquid electrical conductivity

James Bober
Prodigy 20 points
Other Parts Discussed in Thread: LDC1000EVM

Is is reasonable to consider the LDC1000 to measure the electrical conductivity of aqueous solutions of inorganic salts.  After all, the immersing of an inductor bearing an AC current will result in circulating eddy currents through the fluid, the magnitude of which should be proportional to EC.  I'm interested in liquids having an EC in the 1-5 mS/cm range.  What coil geometry would be best suited for this?

Thanks,

Jim

  • 0
    TI__Genius 9300 points
    HI Jim,

    It's feasible, but most likely the coil will have t o be quite big, on the order of 10cm diameter.
    Geometry does not play an important role, as long as its squarish or roundish.
  • 0 in reply to Evgeny Fomin
    Prodigy 20 points
    Funny, but with a LDC1000EVM I substituted a very small inductor fabricated from a ferrite toroidal core (1cm OD, 0.5cm ID, 0.5cm length) with 10 turns on it. Using the LDC1000, I'm measuring an inductance of about 250uH in air. Immersing the core in a couple of KCl solutions (1.4 and 12.9 mS/cm in conductivity, respectively), I'm seeing repeatable measurements in Rp that lead me to believe I can scale Rp to conductivity - at least in that regime. Certainly If I approach the walls of a container, I corrupt the measurements. But by remaining at least several cm from any walls, the measurements are repeatable. I am new to the world of inductive sensing, so am I somehow fooling myself with these experiments?