Here's a simple technique to utilize the Bode Function to create some nice Impedance Plots of various capacitors.
The idea is to have the scope plot Ch2/Ch1, or Vo/Vi as it does with the Bode function. Using an external AWG (SDG2042X) to create the stimulus under LAN control from the SDSX+, place the AWG output signal thru a reference resistor R (1K 2W 1% in our case). The DUT capacitor is placed from the Resistor to Local Ground, and Ch1 senses the AWG side of R and Ch2 senses across the DUT.
Here's a little math behind this, Vo is the voltage across the DUT and Vi is the voltage from the AWG source.
Impedance of DUT Z = Vo/I, where I is the DUT thru current.
I = (Vi-Vo)/R, where R is the sense resistor
Z = Vo/[(Vi-Vo)/R] = R/( Vi/Vo -1), if Vi/Vo is >> 1, then
Z ~ R(Vo/Vi) and Vo/Vi is what the Bode function plots.
So simply scaling the Bode Function dB scale by R revels the ~ Magnitude of DUT Impedance and the Phase is as indicated.
For the magnitude in ohms |Z| ~ R[ 10^(dB/20)], C ~ 1/(|Z|*2pi*F)
Here's a few capacitor examples:
Edit: Added (Calculated from graphs and Tonghui LCR Meter TH2830 Measured values).
#28 680uF Electrolytic (634uf, 641.5uF @ 100Hz)
#31 470uF Polymer (459uF, 469uF @ 1KHz)
#32 10uF Mylar (9.59uF, 9.72uF @ 1KHz)
#33 5uF Polypropylene (4.89uF, 4.84uF @1KHz)
#34 0.1uF Polystyrene (poor quality)
Added these:
#35 1uF Mylar (981.3nF, 994.5nF @ 10KHz)
#37 2uF Polypropylene (1.985uF, 1.975uF @ 10KHz)
#38 10nF Polystyrene (10.28nF, 10.086nF @ 100KHz)
#39 100nF Disc Ceramic (95.9nF, 92.81nF @ 10KHz)
The SDSX+ does a respectable job with it's nice low noise front end and good overall dynamic range, and the Bode Function is "Icing on the Cake"
![Grin ;D](https://www.eevblog.com/forum/Smileys/default/grin.gif)
Anyway, hope some folks find this interesting.
Best,