Current Sensor Integrator Feedback for Drift and Bandwidth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional integrators for Rogowski coil current sensors suffer from drift issues due to input current noise, which reduces their accuracy and bandwidth, especially in applications requiring high precision and wide bandwidth.
Innovation Solution
The use of field-effect transistors (FETs) in the feedback path of the integrator, either as a junction-gate FET (JFET) or metal oxide FET (MOSFET), allows for electronic control of net resistance, minimizing drift while maintaining wide bandwidth through automatic reset and gain control, utilizing frequency discriminators to manage the FET's operation based on signal noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional integrator is used for Rogowski coil current sensors, then the output signal can be integrated to provide current measurement, but drift occurs due to input current noise which reduces accuracy and bandwidth
Solution Approach 1:
The patent applies dynamics by making the feedback resistance variable rather than fixed. A FET (field-effect transistor) is used to dynamically adjust the feedback resistance value based on the input signal characteristics. The FET operates in different regions (ohmic/triode and saturation) to provide different resistance values, enabling the integrator to adapt its behavior to minimize drift while maintaining measurement accuracy and bandwidth.
Solution Approach 2:
The patent changes the resistance parameter of the feedback element from a constant value to a variable value controlled by the FET. By adjusting the FET's gate voltage, the feedback resistance can be changed to optimize the integrator's performance for different signal conditions, thereby reducing drift from low-frequency noise while preserving bandwidth for high-frequency signals.
2Reliability
If the feedback resistance is increased to reduce drift, then drift from low-frequency noise is minimized, but the bandwidth of the integrator is reduced
Solution Approach 1:
The patent uses the FET to dynamically switch between different feedback resistance values based on the frequency content of the input signal. For low-frequency signals where drift is a concern, the FET provides a higher resistance to minimize drift. For high-frequency signals where bandwidth is critical, the FET provides a lower resistance to maintain wide bandwidth. This dynamic adjustment resolves the contradiction between drift reduction and bandwidth preservation.
Solution Approach 2:
The FET is controlled by a periodic square wave signal that switches between two voltage levels. This periodic control causes the FET to alternate between providing high and low feedback resistance values, effectively creating a time-varying feedback resistance that adapts to different frequency components of the input signal, thereby simultaneously addressing drift and bandwidth requirements.
3Measurement precision
If a FET is used in the feedback path to enable variable resistance control, then drift is minimized while maintaining wide bandwidth, but the device complexity increases
Solution Approach 1:
The FET in the feedback path is controlled by a square wave signal that is derived from the integrator's own output through a frequency discriminator circuit. This self-generated control signal enables the FET to automatically adjust the feedback resistance based on the signal characteristics without requiring external control circuitry, thereby minimizing drift while maintaining bandwidth without proportionally increasing overall system complexity.
Solution Approach 2:
The FET serves multiple functions: it acts as a variable resistance element in the feedback path, provides automatic gain control, and enables adaptive drift compensation. By using a single component (the FET) to perform multiple functions, the patent achieves improved measurement precision and drift performance without requiring additional separate control circuits, thus limiting the increase in device complexity.
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 configuration effectively reduces drift from low-frequency noise while preserving the wide bandwidth of the integrator, making it suitable for various applications including current measurements and navigation, and can be adapted for use with Rogowski coils and other sensors.
Implementation Method 1
The use of field-effect transistors (FETs) in the feedback path of the integrator, either as a junction-gate FET (JFET) or metal oxide FET (MOSFET), allows for electronic control of net resistance
Implementation Method 2
The voltage induced in the coil is proportional to the rate of change of current in the conductor
Data Source
AI summary
An integrator for use with a current sensor provides a feedback loop using a frequency discriminator, reducing drift while maintaining wide bandwidth.