I'm probing an RF (~75 MHz) oscillator. I'm trying to measure the voltage drop across a capacitor. (I'm afraid I may be pushing its limits.) When I attach my x10 oscilloscope probes it loads down the circuit some(probe capacitance is 16 pF). Can I add a series capacitor (1-2 pF) to make another voltage divider and turn my probe into ~ x 100 (I'll have to calibrate it from another stiff source.)
I tried it, but it was a massive fail on the first attempt because of the inductance in the long ground lead of the probe... (long is ~10 cm). I made a little ground clip and soldered it on.
And that worked better.
Here's the oscilloscope shot with x10 probes top and bottom of the 2.2 pF cap that I have in series.
Channel 2 (in blue) is the "x100" side. I'm getting what looks like more bandwidth with the x100. This is not too surprising the x10 probe is an HP10071A (bandwidth = 150 MHz). But also the calibration factor is only about x30. 20 Vp-p vs. 7 Vp-p... Is that to be expected?