Dual magnetometer calibration
Examples of systems and methods for calibrating or operating a magnetic sensor for sensor temperature or operating conditions are provided. The magnetic sensor can comprise a dual magnetometer sensor that comprises a first, low-power-consumption magnetometer (e.g., a magneto-inductive magnetometer) and a second higher-power-consumption magnetometer (e.g., a magneto-resistive magnetometer). The second magnetometer can have a lower unit-to-unit variation in temperature calibration parameters and can be used to temperature-correct readings from the first magnetometer. The magnetic sensor can dynamically switch between usage of the first magnetometer and the second magnetometer in order to provide a dynamic sample rate that can depend on conditions within the sensor or external to the sensor.
1. A magnetic sensor comprising:
a first magnetometer having a first modality and a first unit-to-unit variation in a temperature calibration;
a second magnetometer having a second modality and a second unit-to-unit variation in temperature calibration, the second modality different from the first modality, the second unit-to-unit variation smaller than the first unit-to-unit variation;
a temperature sensor; and
a processor programmed to utilize a temperature-calibrated magnetic reading from the second magnetometer to calibrate, at least in part, a magnetic reading from the first magnetometer.
2. The magnetic sensor of claim 1 , wherein the first modality comprises magneto-impedance.
3. The magnetic sensor of claim 1 , wherein the second modality comprises magneto-resistance.
4. The magnetic sensor of claim 1 , wherein the first unit-to-unit variation in temperature calibration is associated with an offset or a gain.
5. The magnetic sensor of claim 1 , wherein the second unit-to-unit variation is smaller than the first unit-to-unit variation by at least a factor of 5, at least a factor of 10, or more.
6. The magnetic sensor of claim 1 , wherein the first unit-to-unit variation exceeds 2 μT at least at some temperatures between −20° C. and +60° C.
7. The magnetic sensor of claim 1 , wherein the second unit-to-unit variation is less than 1 μT at least at some temperatures between −20° C. and +60° C.
8. The magnetic sensor of claim 1 , wherein the first magnetometer has a first power consumption and the second magnetometer has a second power consumption, the second power consumption greater than the first power consumption by a factor greater than 10, a factor greater than 50, a factor greater than 100, or more.
9. A magnetic sensor comprising:
a first magnetometer configured to be sampled at a first sample rate;
a second magnetometer configured to be sampled at a second sample rate different from the first sample rate; and
a processor programmed to:
output magnetic readings from the first magnetometer at the first sample rate;
detect a trigger event; and
switch to output magnetic readings from the second magnetometer at the second sample rate.
10. The magnetic sensor of claim 9 , wherein the first magnetometer comprises a magneto-resistance magnetometer and the second magnetometer comprises a magneto-impedance magnetometer.
11. The magnetic sensor of claim 10 , wherein the first sample rate is less than 50 samples per second and the second sample rate is greater than 100 samples per second.
12. The magnetic sensor of claim 9 , wherein the processor is programmed to:
detect a second trigger event; and
switch to output magnetic readings from the first magnetometer at the first sample rate.
13. The magnetic sensor of claim 9 , wherein the trigger event comprises one or more of: a battery charge level or a magnetic sensor temperature or an indication to provide precision navigation.