This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

Some questions about the LDC1000 Sensor

Hello,

I got a LDC1000 Sensor and have some questions about it:


1. The LDCLK is set to 6 MHz. I read that this is the frequency, that the LDC 1000 will use to count the frequency of the LC-oszillator. Do I have to pay attention to Aliasing? Because in the datasheet there is listed, that I can measure frequencies up to 5 MHz.


2. Can I also use SMD Coils instead of TI Coil Webench? I´ve tested some SMD coils with capacitors which I used by modelling it in Webench. How does target surface dimension influence measurement. I don´t have a circular conductive target (rectangular)?


3. How does sensor frequency influence accuracy. Can I change frequency by the LDC1000 or is it set only by values of L and C?


4. What is the role of the Response time? I choose different Modes, but is it right that this will change sensor frequency (as datasheet explained)?


I would be happy if somebody could help me.
Best Regards,
Tim

  • Hello Tim.

    No, aliasing is not a concern with the implementation. A higher reference frequency means a higher effective inductance measurement.

    Yes, SMD coils can be used, but you need to ensure that an unshielded inductor is used.

    The Sensor frequency is set by the L and C; the LDC does not change the frequency.

    The Response time is the amount of time (number of cycles of the sensor frequency) that the LDC measures the L and RP. It is permitted to change the Response time without changing the sensor frequency ; rather the response time is used to make a trade-off of conversion time vs. effective conversion resolution.

    Regards,

    ChrisO
  • Hello Chris,

    thanks a lot for your answer!

    Best Regards,
    Tim
  • Hello,

    I still got some more questions about LDC1000.

    1. I tried different coils. For this I used SMD inductors with 12µH and 150 pF but the result was quiet bad. I read that the measurement range should be up to 0.5*Diameter of the coil. I tried distances from 1 mm up to 5mm. I want to measure very accurate in range of 1µm. Do I have to design my own coils from TI Webench Coil Designer for this purpose or still use SMD coils? 


     2. How does resistance influence oscillation frequency? As I read in datasheet, you only calculate sensor frequency for Dimension with formula:

    f=1/(2*Pi*sqrt(L*C))

    Why do you not use formula:

    f=(1/2*Pi)*sqrt((1/L*C)-(R/4*L)^2)

    2. Why does LDC1000 regulate constant amplitude and measure Rp by the amount of energy needed to keep this amplitude constant and not just measure amplitude and calculate relationship from Usource to Umeasure?

    3. How does sensor frequency influence accuracy? Do you have any formula for this?
    4. How is the dependence of the shape of the target if I want to use multiple coils at different positions of an rectangular object?

    Thanks a lot for your help!

    Regards,

    Tim