Development of a Hall-sensor based magnetometer.
The goal of this project was the design and construction of a
device that would use a Hall sensor A device that measures or detects a real-world condition, such as motion, heat or light and converts the condition into an analog or digital representation. An optical sensor detects the intensity or brightness of light, or the intensity of red, green and blue for color systems. and the Meisner Effect to measure
the effectiveness of a material as a superconductor A material that has little resistance to the flow of electricity. Traditional superconductors operate at absolute zero (-459.67 degrees Fahrenheit or -273.15 degrees Celsius). Experiments in the 1980s raised the temperature to -321 degrees Fahrenheit. . To understand the
Meisner Effect, it is best to imagine a rock in the middle of a flowing
stream. When a magnetic field is directed toward a superconductor, the
lines of field curve around the material and reform on the other side,
much like the water curves around the rock in the stream. The lines
curving away will also leave an area very close to the superconductor
where there is no magnetic field. Here is where the Hall-sensor is
utilized. A Hall sensor measures the magnitude of magnetic field. The
sensor was placed directly adjacent to the surface of the
superconductor, with a thin layer of grease grease, mixture of lubricant and thickener. It is used to reduce friction between surfaces from which oils would leak away or cause damage by dripping, or where lubrication must be assured for extended periods. Many greases are mixtures of mineral oil and soap. keeping them in contact. A
solenoid solenoid (sō`lənoid'), device made of a long wire that has been wound many times into a tightly packed coil; it has the shape of a long cylinder. of a known calibration calibration /cal·i·bra·tion/ (kal?i-bra´shun) determination of the accuracy of an instrument, usually by measurement of its variation from a standard, to ascertain necessary correction factors. was used to produce a constant magnetic
field toward the superconductor/Hall sensor apparatus. The data from the
sensor was recorded as the temperature of the superconductor was
lowered. A graph of the data over the temperature showed a sharp drop in
the magnetic field once the critical temperature of the superconductor
was reached. Thus, the effectiveness of different materials as
superconductors can be compared by comparing the change in the magnetic
field detected by the Hall sensor once the critical temperature of each
material is reached.
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No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005 Gale, Cengage Learning. All rights reserved.
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