Hi Chester,
The safest way of doing this, as suggested, is to use a clamp-on current probe of some nature - either a clamp-on meter, or a clamp-on probe for a multimeter (
example here ).
If you're going to do this on a number of devices, then you may want to build yourself a handy coupler such as
this one (the loop on the side made specifically for current clamps).
If microwave ovens are your thing, then you may wish to
look here , as microwaves have a serious inrush current (and depending on the design which may use on/off power control, may have such an inrush each time the magnetron is switched on!).
Hope thgis helps.
M.
