| 摘要 |
A three-dimensional magnetic field sensor is used as part of a vehicle detector to monitor plural parking spaces. The detector includes a controller which periodically samples the magnetic field and compares the present field to a prior field. When the difference exceeds a threshold, the change in the field is compared to previously recorded calibration changes to determine which calibration change the present change most closely resembles. The results are displayed to direct customers to vacant parking spaces or to identify spaces which are occupied but whose meters have expired.
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