Non-contact sheet conductivity measurements implementing a rotating magnetic braking system
First Claim
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1. An apparatus for performing a non-contact resistivity measurement of a sheet of material to be measured, the apparatus comprising:
- a magnet coupled to a motor that causes the magnet to move in one of a linear direction and a rotational direction;
a power measuring device configured to determine a first power value used by the motor in moving the magnet when in proximity to the sheet of material, and to measure a second power value used by the motor in moving the magnet when not in proximity to the sheet of material; and
a computing device configured to determine a difference between the first power value and the second power value, wherein the first power value is greater than the second power value due to a magnetic braking effect from an induced eddy current in the sheet by motion of the magnet in proximity to the sheet of material, the computing device using the difference between the first and second power values to compute the resistivity of the sheet of material;
wherein the computing device uses a known distance between the magnet and the sheet of material to compute the resistivity of the sheet of material, and computes the resistivity, σ
S, of the sheet of material in accordance with the expression;
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Abstract
A non-contact sheet conductivity measurement system includes a magnetic head apparatus, a computing system coupled to the magnetic head apparatus, a linear actuator coupled to the magnetic head apparatus, a motor controller coupled to the magnetic head apparatus, a power supply coupled to the magnetic head apparatus and a frequency meter coupled to the magnetic head apparatus.
13 Citations
9 Claims
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1. An apparatus for performing a non-contact resistivity measurement of a sheet of material to be measured, the apparatus comprising:
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a magnet coupled to a motor that causes the magnet to move in one of a linear direction and a rotational direction; a power measuring device configured to determine a first power value used by the motor in moving the magnet when in proximity to the sheet of material, and to measure a second power value used by the motor in moving the magnet when not in proximity to the sheet of material; and a computing device configured to determine a difference between the first power value and the second power value, wherein the first power value is greater than the second power value due to a magnetic braking effect from an induced eddy current in the sheet by motion of the magnet in proximity to the sheet of material, the computing device using the difference between the first and second power values to compute the resistivity of the sheet of material; wherein the computing device uses a known distance between the magnet and the sheet of material to compute the resistivity of the sheet of material, and computes the resistivity, σ
S, of the sheet of material in accordance with the expression; - View Dependent Claims (2, 3, 4, 5)
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6. An apparatus for performing a non-contact resistivity measurement of a sheet of material to be measured, the apparatus comprising:
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a magnet coupled to a motor that causes the magnet to move in one of a linear direction and a rotational direction; a power measuring device configured to determine a first power value used by the motor in moving the magnet when in proximity to the sheet of material, and to measure a second power value used by the motor in moving the magnet when not in proximity to the sheet of material; and a computing device configured to determine a difference between the first power value and the second power value, wherein the first power value is greater than the second power value due to a magnetic braking effect from an induced eddy current in the sheet by motion of the magnet in proximity to the sheet of material, the computing device using the difference between the first and second power values to compute the resistivity of the sheet of material; wherein the computing device uses a known distance between the magnet and the sheet of material to compute the resistivity of the sheet of material, and computes the resistivity, σ
S, of the sheet of material in accordance with the expression; - View Dependent Claims (7, 8, 9)
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Specification