A method for generating alkali metal in a zero oxidation state includes reacting an alkali metal compound having a —S-M substituent, where M is an alkali metal and S is sulfur, with gold in a zero oxidation state to release the alkali metal in the zero oxidation state. For example, an alkali metal alkylthiolate can be reacted with a gold in a zero oxidation state to release the alkali metal in the zero oxidation state. As another example, an alkali metal sulfide can be reacted with gold in a zero oxidation state to release the alkali metal in the zero oxidation state. The alkali metal may be used in various applications including vapor cells, magnetometers, and magnetic field measurement systems.

A method for generating alkali metal in a zero oxidation state includes reacting an alkali metal compound having a —S-M substituent, where M is an alkali metal and S is sulfur, with gold in a zero oxidation state to release the alkali metal in the zero oxidation state. For example, an alkali metal alkylthiolate can be reacted with a gold in a zero oxidation state to release the alkali metal in the zero oxidation state. As another example, an alkali metal sulfide can be reacted with gold in a zero oxidation state to release the alkali metal in the zero oxidation state. The alkali metal may be used in various applications including vapor cells, magnetometers, and magnetic field measurement systems.

One embodiment is a magnetic field measurement system that includes at least one magnetometer having a vapor cell, a light source to direct light through the vapor cell, and a detector to receive light directed through the vapor cell; at least one magnetic field generator disposed adjacent the vapor cell; and a feedback circuit coupled to the at least one magnetic field generator and the detector of the at least one magnetometer. The feedback circuit includes at least one feedback loop that includes a first low pass filter with a first cutoff frequency. The feedback circuit is configured to compensate for magnetic field variations having a frequency lower than the first cutoff frequency. The first low pass filter rejects magnetic field variations having a frequency higher than the first cutoff frequency and provides the rejected magnetic field variations for measurement as an output of the feedback circuit.

One embodiment is a magnetic field measurement system that includes at least one magnetometer having a vapor cell, a light source to direct light through the vapor cell, and a detector to receive light directed through the vapor cell; at least one magnetic field generator disposed adjacent the vapor cell; and a feedback circuit coupled to the at least one magnetic field generator and the detector of the at least one magnetometer. The feedback circuit includes at least one feedback loop that includes a first low pass filter with a first cutoff frequency. The feedback circuit is configured to compensate for magnetic field variations having a frequency lower than the first cutoff frequency. The first low pass filter rejects magnetic field variations having a frequency higher than the first cutoff frequency and provides the rejected magnetic field variations for measurement as an output of the feedback circuit.

A non-metallic layer stranded optical cable with a reversal point capable of being positioned and a detection method thereof, which solves the problems of determining a reversal point of a cable core and performing an operation of drawing out an optical fiber from the optical cable. The present invention relates to a non-metallic layer stranded optical cable, and the key points of the technical solution thereof includes a cable core and a metal film provided at each reversal point of the cable core, and an outer sheath is provided on the cable core.

A system for determining at least one characteristic of a transmitting coil generating a magnetic field may include a first measurement coil being wound in a first direction, a second measurement coil being wound in a second direction, a voltage measuring device, and at least one processor in communication with the voltage measuring device. The first measurement coil and the second measurement coil may be adjacent to one another. The voltage measuring device may be configured to measure a first voltage of the first measurement coil and a second voltage of the second measurement coil in response to the magnetic field generated by the transmitting coil. The at least one processor may be configured to determine the at least one characteristic of the transmitting coil based on a ratio between the first voltage and the second voltage at a predetermined frequency.

A magnetism detection device includes: a transmission line set having a transmission line including a linear first conductor including a magnetic material; and a detector that: inputs, from a first end of the transmission line set, a pulse signal as a first incident wave and detects, at the first end, a first reflected wave of the first incident wave; inputs, from a second end opposite to the first end, a pulse signal as a second incident wave and detects, at the second end, a second reflected wave of the second incident wave; and detects a strength of a magnetic field applied to the transmission line set based on compositing of the first reflected wave and the second reflected wave.

Systems and methods may provide for obtaining first sensor data associated with a gyroscope and obtaining second sensor data associated with a magnetometer. Additionally, the first sensor data, the second sensor data and an extended Kalman filter may be used to calibrate the magnetometer. In one example, a sampling rate of the magnetometer is increased before obtaining the second sensor data and the sampling rate of the magnetometer is decreased after calibration of the magnetometer.

Systems and methods may provide for obtaining first sensor data associated with a gyroscope and obtaining second sensor data associated with a magnetometer. Additionally, the first sensor data, the second sensor data and an extended Kalman filter may be used to calibrate the magnetometer. In one example, a sampling rate of the magnetometer is increased before obtaining the second sensor data and the sampling rate of the magnetometer is decreased after calibration of the magnetometer.

Various embodiments are directed to a method and system for mapping or visualizing the magnetic fields and their associated field strengths of an object, such as a mobile computing device. An example source of the magnetic fields may be a near-field communication (NFC) reader configured in the object. A computer vision system or device may track a visual marker arranged near or on a magnetic field strength detector in order to associate, match, or map the magnetic field strength measurement readings of the detector at different positions or locations on the object. The computer vision system may generate and display a heat map of the object based on at least the magnetic field strength measurements and their relative positions.