A magnetic field strength threshold system including: a sensor responsive (11, S1) to a magnetic field, e.g. from a nuclear magnetic resonance device, and actuating in response to a strength of the magnetic field (MF-1) above a predetermined threshold, the sensor (11, S1) including: a cylindrical housing including a seat support and an electrical contact ring; a pivotable member supported by the seat support of the cylindrical housing for movement through a 360° range of directions, the pivotable member including a magnet responsive to the magnetic field (MF-1) to cause movement of the pivotable member irrespective of direction of incidence of the magnetic field and without consumption of energy provided by an energy source, the pivotable member also including an electrical conductor, movement of the pivotable member responsive to the magnetic field (MF-1) of strength above the predetermined threshold causing the electrical conductor of the pivotable member to electrically engage the electrical contact ring of the cylindrical housing so that electrical energy may flow through the electrical conductor of the pivotable member; and a bias spring being connected between the pivotable member and the cylindrical housing to bias the pivotable member away from an engagement of the electrical conductor of the pivotable member to the electrical contact ring of the cylindrical housing; wherein the pivotable member includes a single spherical ball bearing as a pivot point, located coincident with a center of mass of the pivotable member, the single spherical ball bearing supported by the cylindrical housing seat support, and the bias spring biasing the single spherical ball bearing into engagement with the seat support; and an alarm device operatively connected to the sensor (11, S1) and outputting an alarm, responsive to the sensor actuation, wherein the alarm device is only powered via the sensor actuation by receipt of electrical energy provided from the energy source and electrical connection proceeding through the bias spring, the electrical conductor of the pivotable member and the electrical contact ring of the cylindrical housing responsive to the magnetic field (MF-1) of strength above the predetermined threshold. a cylindrical housing including a seat support and an electrical contact ring; a pivotable member supported by the seat support of the cylindrical housing for movement through a 360° range of directions, the pivotable member including a magnet responsive to the magnetic field (MF-1) to cause movement of the pivotable member irrespective of direction of incidence of the magnetic field and without consumption of energy provided by an energy source, the pivotable member also including an electrical conductor, movement of the pivotable member responsive to the magnetic field (MF-1) of strength above the predetermined threshold causing the electrical conductor of the pivotable member to electrically engage the electrical contact ring of the cylindrical housing so that electrical energy may flow through the electrical conductor of the pivotable member; and a bias spring being connected between the pivotable member and the cylindrical housing to bias the pivotable member away from an engagement of the electrical conductor of the pivotable member to the electrical contact ring of the cylindrical housing; wherein the pivotable member includes a single spherical ball bearing as a pivot point, located coincident with a center of mass of the pivotable member, the single spherical ball bearing supported by the cylindrical housing seat support, and the bias spring biasing the single spherical ball bearing into engagement with the seat support; and an alarm device operatively connected to the sensor (11, S1) and outputting an alarm, responsive to the sensor actuation, wherein the alarm device is only powered via the sensor actuation by receipt of electrical energy provided from the energy source and electrical connection proceeding through the bias spring, the electrical conductor of the pivotable member and the electrical contact ring of the cylindrical housing responsive to the magnetic field (MF-1) of strength above the predetermined threshold.