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LDC1612: LDC1612

david chauvin
Prodigy 60 points
Part Number: LDC1612
Other Parts Discussed in Thread: LDC1101

Hi,

i want to measure a metal composition change with the LDC1612.

My question is then : Can the LDC1612 measure an equivalent of the Rp or proximity data as the LDC1000 did?

If not, Can the LDC1612 measure the energy loss or a target metal composition change? Indeed, measuring fs is dependent of Q so is dependent of the energy loss just as Rp was, right? (with a difference sensitivity maybe). So measuring fs variation, I should be able to measure metal composition change, right? 

I want to use the LDC1612 to measure a change of metal composition (as the Rp of the former LD1000 did). 

Thanks in advance for your answer,

David

  • 0
    TI__Genius 17440 points

    Hi David,

    The LDC1612 cannot measure changes in Rp, only changes in inductance. I would not recommend using L-measurement for a metal detection application. L-measurement provides information about the target metal's permeability and Rp-measurement provides information on the target metal's resistivity. You need both for a robust metal detection application.

    You may wish to consider the LDC1101, which can perform both Rp-measurement and L-measurement.

    Best Regards,

  • 0 in reply to Kristin Jones93
    Prodigy 60 points

    Hi Kristin,

    Thank you very much for your quick and precise answer! I really appreciate it.

    Just a final question, 

    1) If I had no choice than using the LDC1612, The sensor frequency measurement of the LDC1612 is related to Q then to Rp (cf [1]). So, we can assume a sensitivity to the metal resistivity of the ldc1612, right? Or, Am I completely wrong?

    Thanks again for your help,

    David

    [1]  page 35, Equation (1) and (2) of www.ti.com/.../snoscy9a.pdf

  • 0 in reply to david chauvin
    TI__Genius 17440 points

    Hi David,

    Unfortunately you would not be able to use those equations to determine Rp based on the change in inductance, because the Q factor is also changing. Just changing the temperature will significantly impact both Q and Rp, but it will not change the inductance nearly as much. L-measurement shifts at about 30ppm/°C with NP0/C0G grade capacitors, but with a copper target Rp shifts about 3900ppm/°C.

    Best Regards,