如何判别金属物的大小生理学的研究表明，人的听觉对音量的变化是比较迟钝的（对数关系），而对音调的变化是比较敏感的（线性关系），仪器根据上述情况，用音调的高低来判定金属物品的大小，这是有别于其它同类产品的优点，它使我们能够更正确地分辨出不同大小的金属物品。当仪器的探头扫过人体（物体）时，如果发出较低沉的响声，而且探头停留在发声处的上方后这个响声会逐渐消失，我们可以判定它是一件很小的金属，如皮带扣、拉链等。如果发出的声音很尖锐，即使探头停着不动，声音仍然是持续不断的，那就一定是一块较大的金属，如匕首、手枪等。尺寸： 41(L) X 8.5(W) X 4.5(H)cm
The study of how to distinguish the size and physiology of the metal shows that the changes in the volume of the human hearing are relatively slow (logarithmic), and the change in the tone is more sensitive (linear). The instrument is based on the above situation and uses the pitch to determine the size of the metal, which is different from the other products of the same kind. The advantage is that it enables us to distinguish metal objects of different sizes correctly. When the probe of the instrument sweeps over the body (objects), if a lower noise is made, and the probe stops at the top of the sound, the sound will gradually disappear, and we can determine that it is a very small metal, such as belt buckle, zipper, etc. If the sound is sharp, even if the probe stops and the sound is still continuous, it must be a larger piece of metal, such as a dagger, a pistol, etc. Dimensions: 41 (L) X 8.5 (W) X 4.5 (H) cm