Magnetic field sensing for tamper-indicating devices

An authenticatable container tracking system comprising:

• a non-metallic casing;
• a plurality of magnets mounted to the non-metallic casing, the mounting allowing each of the plurality of magnets to conform to a ferrous surface portion of a target container, the mounting and the plurality of magnets being configured to securely attach the non-metallic casing to the ferrous surface portion of the target container,
• the non-metallic casing comprising:
• a three-axis magnetometer having a sleep mode and an active mode, in sleep mode a first level of power is supplied to the three-axis magnetometer, in the active mode, a second level of power is supplied to the three-axis magnetometer, the three-axis magnetometer being configured to detect a magnetic field signature produced by a combination of the plurality of magnets and the ferrous surface portion of the target container and earth's magnetic field;
• a shock sensor;
• a transmitter;
• a processor in electrical communication with the three-axis magnetometer, the shock sensor and the transmitter;
• a memory;
• and
• a power supply configured to provide power to the processor, the shock sensor, the three-axis magnetometer and transmitter,
• the processor is configured to:
• receive a detection indication from the shock sensor;
• trigger the active mode for the three-axis magnetometer based on the detection indication by causing the second level of power to be supplied from the power supply;
• receive detections of the magnetic field signature from the three-axis magnetometer over a measurement period;
• and
• cause the transmitter to transmit the received detections to an external processor,
• the external processor is configured to:
• for each detection of the magnetic field signature, the external processor is configured to:
• convert the detection to a value;
• and
• compare the value with an alarm threshold,
• determine a percentage of detections having the value above the alarm threshold;
• and
• compare the percentage of detections having the value above the alarm threshold with a preset percentage of allowed values above the alarm threshold,
• when the percentage of detections having the value above the alarm threshold is greater than the preset percentage of allowed values above the alarm threshold, the external processor is configured to generate an alert.

An authenticatable container tracking device comprising:

• a non-metallic casing;
• a plurality of magnets mounted to the non-metallic casing, the mounting allowing each of the plurality of magnets to conform to a ferrous surface portion of a target container, the mounting and the plurality of magnets being configured to securely attach the non-metallic casing to the ferrous surface portion of the target container,
• the non-metallic casing comprising:
• a three-axis magnetometer having a sleep mode and an active mode, in sleep mode a first level of power is supplied to the three-axis magnetometer, in the active mode, a second level of power is supplied to the three-axis magnetometer, the three-axis magnetometer being configured to detect a magnetic field signature produced by a combination of the plurality of magnets and the ferrous surface portion of the target container and earth's magnetic field;
• a processor in electrical communication with the three-axis;
• a memory configured to store alarm threshold and a percentage of allowed values above the alarm threshold, the alarm threshold and the percentage being determined during a baseline measurement session;
• and
• a power supply configured to provide power to the processor and the three-axis magnetometer,
• the processor is configured to:
• periodically trigger the active mode for the three-axis magnetometer by causing the second level of power to be supplied from the power supply for a detection session, the detection session having a measurement period;
• receive detections of the magnetic field signature from the three-axis magnetometer over the measurement period;
• after receiving the detection results, the processor is configured to cause the first level of power to be supplied from the power supply to trigger the sleep mode,
• for each detection of the magnetic field signature, the processor is configured to:
• convert the detection to a value;
• and
• compare the value with the alarm threshold stored in the memory,
• determine a percentage of detections having the value above the alarm threshold;
• and
• compare the percentage of detections having the value above the alarm threshold with the percentage of allowed values above the alarm threshold stored in the memory,
• when the percentage of detections having the value above the alarm threshold is greater than the percentage allowed values above the alarm threshold, the processor is configured to generate an alert.