Coil inductance

Discussion in 'The Projects Forum' started by praptiganguly, May 5, 2014.

  1. praptiganguly

    Thread Starter New Member

    May 5, 2014
    I have designed a coil by winding copper wire to get the desired inductance. However, I have to measure the "resonance impedance" of the coil in two conditions.
    1. The coil alone
    2. The coil when a metal plate is brought in front of the coil.

    The demo video i reffered to showed that they used Impedance Analyzer.
    But i do not have the instrument. How else can i measure the Resonance Impedance?
    Thanks in advance for the help.
  2. KL7AJ

    Senior Member

    Nov 4, 2008
    I believe you're referring to the reactance. By definition, at resonance, the circuit impedance will be zero (disregarding series resistance).

    Inductive reactance can be measured a number of ways, either by resonating it with a known value of capacitance, or using a signal generator with a fixed known resistor, and measuring the voltage drop across the resistor and the inductor.
  3. #12


    Nov 30, 2010
    Your question is not clear to me. Saying the opposite of what KL7AJ said, the DC resistance of the wire becomes the impedance of the coil under theoretical conditions.
    Can you elaborate?
  4. wayneh


    Sep 9, 2010
    The impedance of a coil is a function of frequency. It will range from the intercept, the DC resistance at 0 Hz (DC) and will have a slope against frequency that is the inductance. As the frequency rises, the impedance due to frequency will overwhelm the DC resistance and become the dominant component of impedance.

    I have no idea if this answers your question.
  5. MaxHeadRoom


    Jul 18, 2013
    If the inductive reactance is high enough to be meaningful at 50/60hz then you could supply a AC voltage to the coil and measure the current to obtain the impedance in ohms and work back.
    The resistance is in series with the inductive reactance and usually considered negligible.
    Last edited: May 6, 2014