Do you measure it as a circle or a cylinder ?
In the first case, you can do it with edge points, in the second, just measure it manually, then change the number of row / hits.
you have a curved surface.
if you need to rotate the probe do so so that the probe tip is as normal to the surface as possible.
turn your jog box onto probe mode.
put your probe as close to the center of the circle as possible and as flush to the surrounding surface as possible.
create a move point.
use that as the center of your circle.
now take a hit outside the circle by a few thou. Pretend it's kind of like a sample hit. thats your vector.
now open your measured circle dialog and build a circle based on your center point and your vector.
NOW you can use sample hits and adjust your depth accordingly. dont forget to erase the move point.
