It's air testing coins at 7 and 8 inches (with 8" coil) which is pretty good. However, its picking up a 1" safety pin at no more than 1 1/2" away from the coil. I was hoping to be able to detect a piece of jewelry of this size a few inches deeper than 1 1/2". The distance for the safety pin is about the same for the 8 and 4" coils. Coils are brand new. Can someone please tell me if 1 1/2" for a 1" safety pin is normal for this machine? Thanks a heap.