Fluxgate Magnetometer Circuit Linear Torque Measurement
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Solution Overview
Problem
Current fluxgate magnetometers do not provide a direct linear relationship between the magnetic field and applied torque, and are affected by temperature fluctuations, leading to unstable signal measurements.
Innovation Solution
A circuit that magnetically saturates an inductor and measures the duration of current drainage to determine the amplitude and magnitude of the magnetic field, providing a stable and temperature-independent method for force measurement using a magnetoelastic torque sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fluxgate magnetometer is driven to magnetic saturation by alternating current to detect magnetic field changes, then the magnetometer can convert magnetic field into electric signal, but the output voltage does not provide a direct linear relationship with the magnetic field
Solution Approach 1:
The patent changes the measurement parameter from observing output voltage during saturation to measuring the duration of current drainage after saturation is removed. This temporal parameter measurement provides a direct linear relationship with the magnetic field strength, resolving the non-linearity issue of the traditional voltage-based method
Solution Approach 2:
The patent replaces the traditional voltage-based detection mechanism with a time-based measurement mechanism. Instead of measuring electrical voltage during saturation, the system measures the time duration of current drainage, which provides linear proportionality to the magnetic field magnitude
2Measurement precision
If a fluxgate magnetometer operates by observing magnetically induced changes of impedance, then the magnetometer can detect magnetic field, but temperature fluctuations cause undesirable fluctuations in the output signal
Solution Approach 1:
The patent replaces the impedance-based detection method that is sensitive to temperature with a time-duration measurement method. The current drainage time measurement is inherently more stable against temperature variations, as it depends on the magnetic saturation characteristics rather than impedance changes that are temperature-sensitive
Solution Approach 2:
The system uses the inductor's own current drainage characteristics after saturation removal as the measurement signal. This self-contained measurement approach, where the system measures its own relaxation behavior, provides temperature stability because the drainage time is determined by the magnetic field strength rather than temperature-dependent electrical parameters
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate, reliable, and linear force measurements that are independent of temperature fluctuations, resulting in a stable and proportional measurement of the magnetic field and applied force.
Implementation Method 1
a magnetoelastic material affixed to a torque transducer. Application of torque to the torque transducer generates a magnetic field
Implementation Method 2
The fluxgate inductor is driven to magnetic saturation by an alternating current
Data Source
AI summary
A fluxgate magnetometer drive circuit includes a fluxgate inductor that is driven through magnetic saturation by altering voltage pulses. Following each drive pulse, the spurred magnetic energy in the fluxgate is allowed to dissipate by connecting a fluxgate across a fixed reverse voltage. The time for the fluxgate current to decay to zero is measured and is indicative of a magnetic field induced in the torque transducer.