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Original question:

LDC2114EVM: can you have the inductance measurement absolute?

LDC2114EVM: About LDC2114 measured value

user5203911
Intellectual 560 points
Part Number: LDC2114EVM
Other Parts Discussed in Thread: LDC2114

Hello,
The LDC2114 can provide a 12-bit (2's complement) measurement, so I would like to know what the relationship between the actual frequency and this relative value data is.
If the power is turned on with the target placed at a certain position from the coil, the measured value at that position will be zero by the base tracking algorithm, but the relative value at this time, the maximum value (0x7ff) and the Min value of the measurement range How does (0x800) relate to the frequency at zero value?
Supplement as it is not easy to understand.
When the frequency at the target position d = 0.5 ° is 3 MHz, how many frequencies correspond to the Max value and Min value in that state?
Although there are relative values, are there any relations between the frequency at the center value (0x000) and the frequencies at Max (0x7ff) and Min (0x800)?
Is it written in the data sheet of LDC2114 such as data sheet?

I think that the relative values of Max and MIn are determined based on the initial frequency (center frequency).

I apologize for being difficult to understand because I am not good at English

Best regards

  • 0
    TI__Genius 17440 points

    Hello,

    There's no way to determine the physical sensor frequency by using the output data from the LDC2114. As you noted, the initial sensor frequency when the device is turned on will result in an output code of zero. This is true regardless of the initial frequency value; the frequency at power-on is considered the baseline.

    The positive and negative output values show how the current sensor frequency has changed compared to this initial baseline sensor frequency. If the sensor frequency changes significantly, then the device will output the maximum code value.

    Because of the baseline tracking algorithm, the "zero value" frequency changes over time. This also changes the physical frequencies associated with the Min and Max output code values. There's no way to calculate these exact frequencies because the goal of the device is to provide a relative output.

    You might also find section 5 of this document helpful: http://www.ti.com/cn/lit/an/snoa993/snoa993.pdf

    Best Regards,

  • 0 in reply to Kristin Jones93
    Intellectual 560 points

    MS Jones

    Hello!

    I'm sorry for my late reply.
    This is the characteristic of this IC. I was wondering if the range was decided based on the frequency to be read first. For example, if the center frequency is 1 MHz, the 12-bit range width (-2048 to 2047) will be ± 100 kHz. (The range is determined by the ratio from the center frequency)
    I will study the application note that you have introduced. I may contact you again on this matter.

    Best regards