Here's another interesting use case with the SDS800X HD. If one wishes to see a low frequency plot of capacitance vs frequency then an expensive LCR meter is usually required. There were various threads about using the built-in Bode Function to plot Impedance and Admittance using a DSO, see these for details.

https://www.eevblog.com/forum/testgear/capacitive-impedance-plots-with-sds2104x-plus-bode-function/msg4335745/#msg4335745https://www.eevblog.com/forum/testgear/admittance-measurements-with-dso-awg-with-bode-function/msg4491952/#msg4491952Following the analysis in the above threads, the Bode Plot is defined as:

Bode Function Display = Vo/Vi where Vi is the signal created by a coupled signal generator, and Vo is the voltage across the DUT.

If we add a series impedance Zr with the DUT (Z), then (neglecting DSO sensing currents) the DUT current is:

I = (Vi-Vo)/Zr, where Vo is the output or voltage across DUT, and:

I= Vo/Z, and equating I:

Vo/Z = (Vi-Vo)/Zr

Z = Zr(Vo)/(Vi-Vo)

If Vo is << Vi (meaning Zr >> Z), then:

Z ~ Zr(Vo/Vi)

Normally we make Zr a Reference Resistor, but what if we make Zr a Reference Capacitor, what then?

Z ~ Zcr(Vo/Vi), where Zcr is reference capacitance impedance and what if we are interested in Z being just capacitance, thus:

Zc ~ Zcr(Vo/Vi), where Zc = 1/jwC and Zcr = 1/jwCr

1/jwC ~ (1/jwCr)Vo/Vi, and:

C ~ Cr*/(Vo/Vi)

So if we can "fool" the Bode Plot and swap the Ch1 (Vi) with Ch2 (Vo), then:

C ~ Cr*Bode Plot!!

Of course we can just set the Bode Plot Input and Output to Ch2 and Ch1 respective and not need to reverse the probes and "fool" the Bode Plot!!

Ok, now that we've got thru all that, does it work!!

Yep, sure does

Here's an example of a Precision Polystyrene 1uF Reference Capacitor (1.01594uF) and a 100uF Electrolytic Capacitor.

The DUT Capacitance is directly displayed in dB to the Reference Capacitor, so the resulting DUT Capacitance is the product of the display and Reference Capacitor. Note how the effective DUT capacitance begins to drop off with increasing frequency. Results agree well with Lab Bench LCR Meter (TH2830).

DUT Capacitance result is Cr * 10^(Reading/20)

Not a replacement for a plot displaying LCR meter, but in a pinch might help.

Anyway, hope some folks find this useful.

Best,