Thread: N2863B Probe compensation

A Data Sheet for scope probes, N2862B/63B/89A/90A, can be found on Agilent’s web page at;

http://cp.literature.agilent.com/litweb ... 7111EN.pdf.

The data sheet shows the Compensation Adjustments but I found a better way to match the probes. I connected all 4 probes on my DSOX3024 to the Wave Generator output and used it to adjust the high frequency adjustments. The Wave Generator was set to 1 MHz and 2V P-P square wave. Use the “Prob Comp” output to perform the low frequency coarse adjustment on each probe first. Then connect all 4 probes to the Wave Generator output and overlap the traces. I adjusted the potentiometer that’s closest to the BNC for the flattest, most square edge. The other potentiometer adjusted the delay but also changed the over/under shoot. The low frequency adjustment can be used to tweak the amplitude. Adjust both potentiometers and the low frequency trimmer capacitor so that all 2 or 4 traces overlap. The trigger was set to display both edges and the probes were set for DC.

The WAVGEN output from the scope just doesn't have a short enough rise time to properly compensate these probes for high frequency.

Try adjusting the probes as described. Then look a square wave with about 5 nanosecond rise time with the probes and compare this with the 50 ohm input to the scope. What you will see is that the probes do not accurately reproduce the square wave. There may be ringing or undershoot depending on the settings.

You have to use a external square wave generator with a rise time that is fast enough. How fast is optimal? I don't know. The best I have here is around 5 nanoseconds. I adjust the probes to match the waveform seen with the 50 ohm scope input. (my sig gen is 50 ohms).

Then I carefully adjust the trimmer nearest the scope to so that the scope bandwidth with the probe is about the same as the bandwidth of the 50 ohm input. It takes very little adjustment at this point.

I am not entirely sure this is the proper procedure and I would like to know what others think.

The probe trimmer nearest the scope seems to compensate for the highest frequencies.
The probe trimmer further from the scope (in the box at the base of the probe cable) seems to compensate for the mid frequencies.