C-V current of reverse biased diode

I added a circuit that adds AC signal with Magnitude of 25 mV a variable DC signal between 0 to 5 using with op amp, and applied to a diode. I will measure the AC current through the diode with a lock in amplifier. I will use lock in amplifier built in function generator and auxillary output port behind it. From this experimental setup how can I measure C-V current of a reverse biased diode.

If you are applying an AC signal then you need an oscilloscope to observe waveforms.

You can set the trace to start a sweep when triggered by an external signal as you apply it to the diode.

Or you can set the beam to show X/Y display. It will automatically create a graph-like display of the signal coming to the vertical input, versus the signal coming to the horizontal input.

Does your diode have a reverse V rating of 50V or higher? You may not read anything if you apply 5V reverse bias, not even a microamp.