From Digital and Analogue Instrumentation: Testing and Measurement

14.7 Hall effect devices

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.

Figure 14.40: The Hall effect

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...

Products & Services
Hall Effect Position Sensors
Hall effect position sensors are non-contact devices that convert energy from a magnetic field into an electrical signal. They use the Hall effect, a voltage caused by current-flow in the presence of a magnetic field.
Rotary Position Sensors
Rotary position sensors include potentiometers, resolvers and a variety of magnetic and capacitive technologies. Sensors are designed for angular displacement less than one turn or for multiturn displacement.
Gaussmeters are instruments designed to measure extremely high level magnetic fields.
Hall Effect Proximity Sensors
Hall effect proximity sensors are used to detect the proximity, presence or absence of a magnetic object using a critical distance.
Magnetic Speed Sensors
Magnetic speed sensors rely on a magnet as the sensing element or sensed target to capture rotational or linear speed. They are typically used as gear tooth speed sensors or incorporated into stroboscopes or tachometers.

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