The mass of a body measures the quantity of matter that it contains, while the weight measures the force with which the planet attracts it.

   The weight of a body is the force with which the planet attracts it. Its value is: F=m·g  where g is the intensity of  gravity,  that is, the force experienced by the unit of mass. 

   Mass always has the same value, while weight depends on the value of g, which is not identical in all places.

	The scales measure mass, because on both sides the value of g is the same.
	The dynamometer measures force. If it is used to measure weight, it will give different values depending on the altitude of the place we are in or the planet we are on.

   If you still don't understand the difference between mass and weight revise the experiment here.