this may be relevant to the measurement problem in this thread:
While I was tracing why my 2465B would not switch the sensitivity readout when a 10X probe was connected to Ch1, I stumbled on the following:
When I have both Ch1 and Ch2 active, with only a signal on Ch2, and I press Measure, followed by Frequency, it will give this error because it will try to measure Ch1.
With only Ch2 active and having an input signal, it does read the correct frequency.
And the extra I found today:
The outer ring on all BNC inputs is normally used to switch the readout from 1x to 10x when using a 10x probe with a readout PIN.
However: temporarily grounding the readout ring on any of the 4 channels will trigger an automatic frequency measure of the lowest channel active... This was completely new to me?
BTW, my problem was just a dirty ring on Ch1... ;-)