Devices to measure the force between magnets include simple force scales, piezo crystals for precise measurements, and spring scales. The force varies based on the magnets' geometry and relative positions, but constraining their motion can yield accurate readings. Using a tube to hold bar magnets allows for effective measurement with a spring scale or load cell. An alternative method involves hanging weights to determine the force required to break the magnetic grip. Understanding these measurement techniques is essential for accurate assessments of magnetic interactions.