Thank you bdunham7,
it does measure it if I put the entire waveform on the screen but as per my oy original post then the resolution is very low. I needed to measure it with a high precision (as high as possible, ideally 4 or more decimal digits).
OK, I thought you weren't even getting the two decimals. The measurements in the menu are done with the on-screen information, so the precision is quite limited, I'm guessing you see something like 2.00 Hz, or even 2.0 Hz (which would be pretty crappy) and you want 2.0000. It appears that neither of your instruments will give you what you want directly and you either have to use cursors, which will likely be no more precise, or some workaround like running your test signal into CH1 and your AWG into CH2 and then adjusting the AWG output to exactly overlap your test signal. That should give you the precision you want. That' s the best idea I've got.