US Patent 10147289 Magnetic field sensing for tamper-indicating devices

Sensing devices, systems and methods for securing articles against tampering using a unique magnetic field signature measured at two different times are provided. One or more sensing devices are secured to a ferrous surface portion of a target container. The sensing devices are secured using a plurality of magnets. The unique magnetic field signature sensed by a sensing device is produced by a combination of the plurality of magnets of the sensing device and the ferrous surface portion of the target container and earth's magnetic field. The two different times being one of a baseline measurement session and one of an observation measurement session. An observation measurement session may be triggered by a shock event or periodically.