Developing an impedance meter to measure DUT

Discussion in 'The Projects Forum' started by c1rcu1ts, Dec 23, 2015.

  1. c1rcu1ts

    Thread Starter Member

    Oct 19, 2013
    62
    0
    Hello everyone,

    I am simply asking if there is another way to measure the impedance besides the wheatstone bridge method. I am curious if there is actually an integrated circuit capable of measuring impedance.

    I have intentions of creating a waveform using PWM from a microcontroller (Arduino Mega 2560 R3) and sending it to a DUT to measure the impedance. The DUT is actually a liquid solution that should have capacitive, inductive and resistive elements.

    I am looking to design for frequencies up to about 1MHz.

    Thank you.
     
  2. DickCappels

    Moderator

    Aug 21, 2008
    2,651
    632
    You can make impedance measurements by driving the device under test with a sine wave of the desired frequency through a current source, then measuring the amplitude of the resulting waveform.

    The simple case is the current source, where ZDUT = V/I.

    If you take two measurements of integrated half cycles what are 90° out of phase with one-another you can determine the magnitudes of the real and imaginary parts of the impedance.

    [​IMG]
     
    c1rcu1ts likes this.
  3. c1rcu1ts

    Thread Starter Member

    Oct 19, 2013
    62
    0
    Thank you,

    In the RF I-V method for measuring impedance i guess this would get rid of the current sensing resistor.

    [​IMG]
     
  4. DickCappels

    Moderator

    Aug 21, 2008
    2,651
    632
    There are many ways to measure impedance. The best method for your project depends upon what you want to know about the impedance being measured, what kinds of circuits are available to you (For example, the method in your post #3 might be tricky with a microcontroller.), the degree of desired accuracy, and of course how much work and money you want to put into it.
     
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