Displacement tamper sensor and method
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United States of America Patent
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Jun 7, 2016
Grant Date -
Jun 20, 2013
app pub date -
May 3, 2012
filing date -
Dec 19, 2011
priority date (Note) -
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status (Latency Note)
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Abstract
A displacement sensor for sensing displacement of a first surface relative to a second surface includes a coil mounted on the first surface, and encircling a region in plane; and a conductor extending lengthwise from the second surface through the region. The conductor has a volume that varies along its length. An AC source drives the coil to generate a magnetic field that pierces the region and induces eddy currents in the conductor. Eddy current losses resulting from the eddy currents vary in dependence on the volume of the conductor above and beneath the plane. A sensing circuit is coupled to the AC source to detect changes in eddy current losses, and thereby displacement. Detection of displacement may be used to signal tamper/intrusion. The sensor may further include a visual or audible output to signal such displacement.
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International Classification(s)
- H02J:CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR D....
- G06F:ELECTRIC DIGITAL DATA PROCESSING
- G01R:MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC V....
- G01B:MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIME....
- F16H:GEARING
- G01D:MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VAR....
- H02H:EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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