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Original question:

AFE4300: AFE4300 How to Measure / Calculate Resistance and Reactance

AFE4300: How to Measure / Calculate Resistance and Reactance

JeffP
Prodigy 140 points
Part Number: AFE4300

I asked this question 4 years ago and never got an answer so I'll try again.

Reviewing all the available documentation and forum activity for the AFE4300, I don't see any information on how to directly measure or calculate the Resistance and the Reactance using the AFE4300.

So my question is how to measure Reactance and Resistance?  To make it more simpler, lets just concentrate on a frequency that is supported in both IQ and FWR mode such as 64 kHz.

  • 0
    TI__Mastermind 49766 points

    Hello Jeff,

    Please refer to the application note https://www.ti.com/lit/an/sbaa202/sbaa202.pdf for the impedance measurement using AFE4300.

  • 0 in reply to Praveen Aroul
    Prodigy 140 points

    I know how to get the impedance measurement using the AFE4300.  I am specifically asking if the AFE4300 can measure RESISTANCE and REACTANCE.  Many BIA formulas use Resistance and/or Reactance in the formulas.

  • 0 in reply to JeffP
    TI__Mastermind 49766 points

    AFE4300 in IQ mode provides the complex impedance as a voltage. After calibration, you can convert the voltage to an impedance in polar form.

    Once you know the complex impedance in polar form, you can convert to the rectangular form (R + j X)

  • 0 in reply to Praveen Aroul
    Prodigy 140 points

    I think I’ve figured out how to calculate Reactance and Resistance using the AFE4300.  I wanted to post this solution in case anyone else is having problems attempting to measure Reactance and/or Resistance as this question has been posted multiple times on this forum with no posted solution.

    The method I am using utilizes the Impedance Triangle and the IQ mode of the AFE4300.  Because it uses the IQ mode, it can only measure Reactance and Resistance for the valid IQ frequencies; 8, 16, 32, 64, and 128 kHz.

    Using the IQ mode, the AFE4300 can measure the Impedance (Z) and the Phase Angle at a given frequency.  Once we know these 2 values, we can use some simple trigonometry with the Impedance Triangle to calculate Reactance (X) and Resistance (R) as follows:

    X = Z * sin(Phase_Angle)

    R = sqrt(Z2 - X2)