Moving vs stationary b field

[aniccame]

Is there any known detector that can distinguish between a time varying B field (like an electromagnet driven with an alternating current) and a moving, space varying, B field?

[spacecase0]

if it is pointed vertically and rotating around a vertical axis, an electrometer can tell. but you are going to either need a very sensitive one, or a very strong field.

I am curious as to other options myself.

my next build should give me a moving, space varying, B field. So I will have something to test on.
I already have the same format in a time varying B field (that did not do what I want), so I get to compare.