I am trying to understand all the plots shown in the Waveforms Impedance measurement below. It was made on an Electronics Explorer board, AWG1 to a 1 kohm resistor to a 245 nF capacitor to GND. Scope1 is on the AWG1 output and Scope2 is on the R-C connection. I am measuring a 245 nF capacitor by sweeping from 20 Hz to 20 kHz. (The capacitor is actually four 0.1 uF ceramic caps in parallel that total a measured 245 nF.) Notice on the Impedance plot at 20 Hz that Rs = 2.5 kohm and Xs = |Z| = 30 kohm (the two plots are on top of each other). Notice on the Nyquist plot at 20 Hz that (Rs, Xs) is indicated as (-2.5k, -30k).
I think that since Xs is capacitive reactance it makes sense it has a negative sign. But then shouldn't the Impedance plot say "|Xs|" (magnitude of Xs) as the plot label instead of "Xs" to indicate that the plot is always positive?
Shouldn't the Nyquist plot indicate Rs as +2.5 kohm (in quadrant 4) instead of -2.5 kohm (in quadrant 3)?
Why does the Inductance plot indicate negative hundreds of Henrys?
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Rick314
I am trying to understand all the plots shown in the Waveforms Impedance measurement below. It was made on an Electronics Explorer board, AWG1 to a 1 kohm resistor to a 245 nF capacitor to GND. Scope1 is on the AWG1 output and Scope2 is on the R-C connection. I am measuring a 245 nF capacitor by sweeping from 20 Hz to 20 kHz. (The capacitor is actually four 0.1 uF ceramic caps in parallel that total a measured 245 nF.) Notice on the Impedance plot at 20 Hz that Rs = 2.5 kohm and Xs = |Z| = 30 kohm (the two plots are on top of each other). Notice on the Nyquist plot at 20 Hz that (Rs, Xs) is indicated as (-2.5k, -30k).
I think that since Xs is capacitive reactance it makes sense it has a negative sign. But then shouldn't the Impedance plot say "|Xs|" (magnitude of Xs) as the plot label instead of "Xs" to indicate that the plot is always positive?
Shouldn't the Nyquist plot indicate Rs as +2.5 kohm (in quadrant 4) instead of -2.5 kohm (in quadrant 3)?
Why does the Inductance plot indicate negative hundreds of Henrys?
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