Methods and apparatus to determine an operational status of a device

A computing system, comprising:

• a sensor configured to measure a first magnetic field including a device magnetic field caused by a physical cable attached to an electrically-connected device;
• an environmental sensor configured to measure an environmental magnetic field associated with an audience measurement environment;
• at least one memory storing computer-readable instructions;
• and
• at least one processor configured to execute the computer-readable instructions to perform operations comprising:
• measuring, at the sensor, a first magnetic field, the first magnetic field including the device magnetic field;
• measuring, at the environmental sensor, a second magnetic field associated with the environmental magnetic field and that is different than the device magnetic field;
• and
• determining an operational status of the electrically-connected device based on the device magnetic field.

An article of manufacture comprising computer-readable instructions that, when executed, cause at least one processor to perform operations comprising:

• measuring a first magnetic field, the first magnetic field including a device magnetic field caused by an electrically-connected device;
• measuring a second magnetic field associated with an audience measurement environment having an environmental magnetic field different than the device magnetic field;
• and
• determining an operational status of the electrically-connected device based on the device magnetic field.