TABLE OF CONTENTS The basic Hall sensor is simply a small sheet of semiconductor material. A constant voltage source forces a constant bias current to flow in the semiconductor sheet. The output, a voltage measured across the width of the sheet, reads near 0 if a magnetic field is not present. If the biased Hall sensor is placed in a magnetic field oriented at right angles to the Hall current, the voltage output is in direct proportion to the strength of the magnetic field. This is the Hall effect, discovered by E.H. Hall in 1879 (see Figure 14.40). When a magnetic field, B, is applied to a specimen (metal or semiconductor) carrying a current I c, in the direction perpendicular to I c, a potential difference, V H, proportional to the magnitude of the applied magnetic field B appears in the direction perpendicular to both I c and B. This relationship is expressed in the form:
where K represents a constant, the product sensitivity, which depends on the physical properties and dimensions of the material used for the Hall effect device.
The basic Hall sensor [30] essentially is a transducer that will respond with an output voltage if the applied magnetic field changes in any manner. Differences in the response of devices are generally related to tolerances and specifications, such as operate (turn on) and release (turn off) thresholds, as well as temperature ranges and temperature...
