"Dave M" wrote in message
...
I'm genuinely interested in learning if the technique that I used for years
in calibration labs was, in fact, correct or totally wrong. The technique
that we used was this:
Using a high bandwidth scope, measure its risetime without the probe being
connected (scope connected directly to a fast-rise pulse generator).
Connect the probe being calibrated to the scope input, and connect the probe
tip directly to the pulse generator output.
Measure the resulting pulse risetime.
Using the formula that I gave previously (rearranged to find the probe's
risetime), calculate the probe's risetime and bandwidth.
This method of measuring the performance of a probe worked quite well for
the lab and our customers for the years that I was a cal technician
(commercial and military).

If all you have available is a pulse generator, this is a decent enough
method -- just know that the formula to convert between rise time and
bandwidth assumes a single-pole frequency rolloff, which is usually -- but not
always -- a reasonable assumption.

A more insightful means of measuring scope bandwidth is to take an RF
generator that can produce a repetitive frequency sweep (with a leveled
output), have the start of it trigger the scope, and then adjust the timebase
settings so that you get, e.g., 10MHz or 100MHz or some other convenient MHz
sweep per division. In other words, the scope's display effectively becomes a
Bode plot of the system (scope + probe combined) response.

---Joel