Hall Effect Devices

If ;i magnetic field is applied perpendicular to a current flow in any conductor, the moving charges (which constitute the current) are deflected sidewise and build up a potential difference between the two sides of the conductor. The creation of this transverse electric field (perpendicular to both the magnetic field and the original current flow) is called the Ilall effect. During recent years, interest in this effect has increased tremendously. Before semiconductors and their capabilities were understood, the Hall effect in solids was little more than a laboratory curiosity. Now it is not only an important tool in metallurgy and semiconductor device development, but it has been the mode of operation of many proposed devices. This article describes how 20 or so of these devices operate. In each case, the major advantages or disadvantages are mentioned, but no attempt is made actually to determine the usefulness of the device. The devices to be discussed have been arbitrarily divided into two groups: devices which use a constant magnetic field and devices in which a signal or an oscillator produces at least a part of the magnetic field. Such a division is not entirely arbitrary, because the first group inherently has a very high limit on the operating frequency and the second group has a considerably lower limit. The devices are listed on the following page. 853