All -
I am trying to calibrate one of these generators and I can't seem to make it past step 29 in the calibration procedure. The procedure reads:
Flatness
23. Set the HP 8116A frequency to 2.99 MHz.
24. Connect the HP 8116A's main output to the oscilloscope via a
6 dB attenuator and set the channel attenuation-factor to 2.
25. Connect the HP 8116A's trigger output to the oscilloscope's
trigger input via a 20 dB attenuator.
26. Set the oscilloscope to 160 mV/div and 100 ns/div.
27. Record the ampltude of the output signal.
28. Set the HP 8116A frequency to 9.99 MHz.
29. Check that the output amplitude has decreased by between 2%
and 4% of the amplitude at 2.99 MHz. If not, you must change
the values of both A1R220 and A1R223 (both must have the
same value). Refer to Table 9-1.
However, my amplitude decreases by more then 5%. I have tried three different slope ICs (out of various generators I have) and some produced better flatness then others, but none met spec. I also tried the same procedure on a different generator (also in need of calibration) and it too failed, but not as badly. I have tried the test on two oscilloscopes with the same results. Finally, I tried increasing the value of R220 and R223, but that, too, didn't seem to help, at least not enough. Any other ideas?
As a final note, at these high-frequencies the triangle wave gets rounded-off at the peaks. I have been measuring the amplitude to the actual peak of the waveform, not where the triangle wave would peak if it was not rounded. I assume this is correct...
Thanks in advance!
Matthew
medasaro