Interface configurations for a wearable sensor unit that includes one or more magnetometers
An exemplary magnetic field measurement system includes a wearable sensor unit that includes a magnetometer and a twisted pair cable interface assembly electrically connected to the magnetometer.
1. A magnetic field measurement system comprising:
a wearable sensor unit comprising:
a magnetometer, and
a twisted pair cable interface assembly electrically connected to the magnetometer; and
a controller configured to interface with the magnetometer by way of the twisted pair cable interface assembly;
wherein the twisted pair cable interface assembly comprises at least one of:
a first twisted pair cable interface electrically connected to an input of a light source in the magnetometer, the controller being configured to supply a first drive current to the light source by way of a first twisted pair cable connected to the first twisted pair cable interface;
a second twisted pair cable interface electrically connected to an input of a heater for the light source, the controller being configured to supply a second drive current to the heater for the light source by way of a second twisted pair cable connected to the second twisted pair cable interface;
a third twisted pair cable interface electrically connected to an output of a thermistor for the light source, the controller being configured to read an output of the thermistor by way of a third twisted pair cable connected to the third twisted pair cable interface;
a fourth twisted pair cable interface electrically connected to an output of a monitor photodetector configured to monitor a behavior of the light source, the controller being configured to read an output of the monitor photodetector by way of a fourth twisted pair cable connected to the fourth twisted pair cable interface;
a fifth twisted pair cable interface electrically connected to an input of a heater for a vapor cell of the photodetector, the controller being configured to supply a third drive current to the heater for the vapor cell by way of a fifth twisted pair cable connected to the fifth twisted pair cable interface; or
a sixth twisted pair cable interface electrically connected to an output of a signal photodetector configured to detect light that passes through the vapor cell, the controller being configured to read an output of the monitor photodetector by way of a sixth twisted pair cable connected to the sixth twisted pair cable interface.
2. The magnetic field measurement system of claim 1 , wherein:
the twisted pair cable interface assembly is configured to connect to a twisted pair cable that is also connected to the controller; and
the controller is configured to interface with the magnetometer by at least one of
transmitting signals to the magnetometer over the twisted pair cable, or
receiving signals from the magnetometer over the twisted pair cable.
3. The magnetic field measurement system of claim 1 , wherein the wearable sensor unit further comprises a magnetic field generator configured to generate a compensation magnetic field configured to actively shield the magnetometer from ambient background magnetic fields.
4. The magnetic field measurement system of claim 3 , wherein:
the wearable sensor unit further comprises a coaxial cable interface assembly electrically connected to the magnetic field generator;
the coaxial cable interface assembly is configured to connect to a coaxial cable that is also connected to the controller; and
the controller is configured to supply a drive current to the magnetic field generator over the coaxial cable.
5. The magnetic field measurement system of claim 3 , wherein:
the magnetic field generator comprises a plurality of conductive windings comprising:
a first conductive winding arranged in a first plane, and
a second conductive winding arranged in a second plane that is substantially parallel to the first plane;
the plurality of conductive windings are configured to generate, when supplied with one or more drive currents by the controller, a first component of the compensation magnetic field, the first component of the compensation magnetic field configured to actively shield a magnetic field sensing region from the ambient background magnetic fields along a first axis that is substantially orthogonal to the first plane and the second plane; and
the magnetometer is located within the magnetic field sensing region.
6. The magnetic field measurement system of claim 1 , wherein:
the magnetometer comprises a plurality of magnetometers; and
the controller is a single controller configured to generate a single clock signal; and
use the single clock signal to interface with the magnetometers and the magnetic field generator.
7. The magnetic field measurement system of claim 1 , wherein the controller is remote from the wearable sensor unit.
8. The magnetic field measurement system of claim 7 , wherein the controller is implemented by a computing device not configured to be worn by a user.
9. The magnetic field measurement system of claim 7 , wherein the controller is included in a wearable device configured to be worn by a user and separate from the wearable sensor unit.
10. The magnetic field measurement system of claim 1 , wherein the controller is housed within a single housing.
11. The magnetic field measurement system of claim 1 , wherein the controller is included within the wearable sensor unit.
12. The magnetic field measurement system of claim 1 , wherein:
the magnetometer comprises a photodetector; and
the controller comprises a differential signal measurement circuit configured to measure current output by the photodetector.
13. A wearable sensor unit comprising:
a magnetometer;
a twisted pair cable interface assembly electrically connected to the magnetometer, the magnetometer configured to interface with a controller by way of the twisted pair cable interface assembly;
wherein the twisted pair cable interface assembly comprises at least one of:
a first twisted pair cable interface electrically connected to an input of a light source in the magnetometer, the controller being configured to supply a first drive current to the light source by way of a first twisted pair cable connected to the first twisted pair cable interface;
a second twisted pair cable interface electrically connected to an input of a heater for the light source, the controller being configured to supply a second drive current to the heater for the light source by way of a second twisted pair cable connected to the second twisted pair cable interface;
a third twisted pair cable interface electrically connected to an output of a thermistor for the light source, the controller being configured to read an output of the thermistor by way of a third twisted pair cable connected to the third twisted pair cable interface;
a fourth twisted pair cable interface electrically connected to an output of a monitor photodetector configured to monitor a behavior of the light source, the controller being configured to read an output of the monitor photodetector by way of a fourth twisted pair cable connected to the fourth twisted pair cable interface;
a fifth twisted pair cable interface electrically connected to an input of a heater for a vapor cell of the photodetector, the controller being configured to supply a third drive current to the heater for the vapor cell by way of a fifth twisted pair cable connected to the fifth twisted pair cable interface; or
a sixth twisted pair cable interface electrically connected to an output of a signal photodetector configured to detect light that passes through the vapor cell, the controller being configured to read an output of the monitor photodetector by way of a sixth twisted pair cable connected to the sixth twisted pair cable interface.
14. The wearable sensor unit of claim 13 , wherein:
the twisted pair cable interface assembly is configured to connect to a twisted pair cable that is also connected to the controller; and
the controller is configured to interface with the magnetometer by at least one of
transmitting signals to the magnetometer over the twisted pair cable, or
receiving signals from the magnetometer over the twisted pair cable.
15. The wearable sensor unit of claim 13 , further comprising a magnetic field generator configured to generate a compensation magnetic field configured to actively shield the magnetometer from ambient background magnetic fields.
16. The wearable sensor unit of claim 15 , wherein:
the wearable sensor unit further comprises a coaxial cable interface assembly electrically connected to the magnetic field generator;
the coaxial cable interface assembly is configured to connect to a coaxial cable that is also connected to the controller; and
the controller is configured to supply a drive current to the magnetic field generator over the coaxial cable.
17. The wearable sensor unit of claim 15 , wherein:
the magnetic field generator comprises a plurality of conductive windings comprising:
a first conductive winding arranged in a first plane, and
a second conductive winding arranged in a second plane that is substantially parallel to the first plane;
the plurality of conductive windings are configured to generate, when supplied with one or more drive currents by the controller, a first component of the compensation magnetic field, the first component of the compensation magnetic field configured to actively shield a magnetic field sensing region from the ambient background magnetic fields along a first axis that is substantially orthogonal to the first plane and the second plane; and
the magnetometer is located within the magnetic field sensing region.
18. The wearable sensor unit of claim 13 , wherein:
the magnetometer comprises a plurality of magnetometers; and
the controller is a single controller configured to
generate a single clock signal; and
use the single clock signal to interface with the magnetometers.
19. The wearable sensor unit of claim 13 , wherein the controller is remote from the wearable sensor unit.
20. The wearable sensor unit of claim 13 , wherein the controller is included within the wearable sensor unit.