impedance measurement

Discussion in 'The Projects Forum' started by kaushikgreat, Feb 9, 2009.

  1. kaushikgreat

    Thread Starter New Member

    May 22, 2008
    9
    0
    Hello
    I am a newbie in here and have not much info regarding the electrical stuff. I presently am planning to do some EIS measurements and i wish to find the impedance of the cell that i built. Need to obtain the nyquist plots. ( the plot of Im(Z) Vs Re(Z) ). I do not have access to equipments like analyzers etc. Want to do it from the basics using multimeters, RLC meter and some calculations...
    is there a way i could go about my project?
     
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287

    There's always a way! People were doing this long before anything like network analyzers were available.

    What frequency range are you lookinig at? A signal generator and an R.F. bridge can probably do the trick for you.

    eric
     
  3. kaushikgreat

    Thread Starter New Member

    May 22, 2008
    9
    0
    well, i am looking at broad frequency range, from 1Hz to 100kHz.
    I do have a LCR meter, AC signal generator, few multi meters, resistance box stuff like that.
    And what about the RF bridge ;). no clue there..
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
    An RF bridge, (often known as just an R-X bridge) will allow you to determine the impedance of just about any unknown circuit at one frequency.

    However, you're using pretty low frequencies, so you could probably build a bridge to do what you want pretty simply.

    eric
     
  5. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
  6. kaushikgreat

    Thread Starter New Member

    May 22, 2008
    9
    0
    thanks a lot for that. That was very helpful. I am sure i can do some thing like that, but not sure how do do the adjusting with the resistance that i have. As the text specifies to balance the capacitance part, i need to have an adjustable capacitor component which apparently i don't have. is there another deice i could look at to consider that? i can always buy cheaper instruments..
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    A Q meter is easier to construct, calibrate and use, especially from discreet instruments, than a full RF bridge and may be adequate for your purposes.

    I also think you will have to split your measuring range, frequency wise.

    Low RF (greater than 30khz)
    Audio (less than 30kHz)
    Powerline (less than 400Hz)

    are the usual splits.
     
  8. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
    Alas...I used to have a Heathkit Q meter, which I sold for a song about 30 years ago. Now they're getting a pretty penny for the gems on Ebay.

    Oh well....

    eric
     
  9. kaushikgreat

    Thread Starter New Member

    May 22, 2008
    9
    0
    oh well thanks for the inputs, will look into them and come back after i assemble the stuff.!
    I just require to take discreet measurements and read out/find out the impedance.
     
Loading...