Characteristic impedance of AWG 33 copper magnet wire

[Baluncore]

Experiment; Measure the L at low frequency to hide the C. Measure the C at highest frequency to hide the L. Measure R at DC. Model the solenoid as a series RL in parallel with a lump of C.
Compute the self resonant frequency and the Q. Compare them with your measured graphical data.


Your measured characteristics are plotted across frequency. The turn-on and turn-off edges of the driver have broad-band characteristics.

When turning on, there is a high current peak as the driver short circuits the terminal C, then the inductor current starts to rise towards the R limited value. When turning off, the coil voltage slews at a rate determined by terminal L and C, but only as far as the flyback diode permits.

The importance of particular solenoid characteristics will not be known until you draw the circuit diagram of the solenoid and it's driver. What circuit will you use? What magnetic paths will you model?

 

[jsgruszynski]

I am working on impedance measurements of close-wound electromagnetic coils. I am using an Agilent LCR meter to measure the impedance of these coils over a frequency range of 20Hz-2MHz. When I perform the measurements, I get impedance magnitude and phase angle in degrees. I would like to construct a Smith chart of these measurements, but I am unsure of how to measure the characteristic impedance of the coils. These are single strand, AWG 33 copper wires - diameter of approximately 180μm including the insulation. Thus, they are not traditional transmission lines, based on my understanding. What is the best method to measure the characteristic impedance of these coils? Is it simply the DC resistance? Thanks for your help.

You should likely choose a characteristic impedance of 50 ohms - it's not a feature of the device but of everything you connect it to which usually is 50 ohms. The impedance you measure simply is plotted per the formula for Gamma (complex reflection coefficient). A Smith Chart is merely a plot of the Gamma definition plotted from cartesian impedance (aka a conformal map). Each impedance you measure on the LCR meter can be plotted directly using the coordinates on the Smith Chart or you can plot the results of Gamma as points on a complex plane - same same.