Application Cases

Experiment Name: Research on Testing and Analysis Techniques of Power Amplifiers Based on Micro-Fluxgate with Porous Iron Core

Experiment Objective:
This section focuses on testing a 3D solenoid-type micro-fluxgate with a porous iron core, optimized through topology and fabricated using MEMS technology. A series of performance metrics, including sensitivity, linear range, noise, and remanence error, were measured under varying external magnetic fields, excitation current values, and excitation frequencies.

Experimental Equipment:
Signal generator, ATA-4011 high-voltage power amplifier, magnetometer, ammeter, fluxgate, oscilloscope, spectrum analyzer, etc.

Experimental Procedure:
The excitation signal for the fluxgate was generated by cascading an arbitrary signal generator and the power amplifier ATA-4011. An ammeter was connected in series in the excitation circuit to measure the magnitude of the excitation current. A DC power supply was used to energize the solenoid, generating the external magnetic field under measurement, with the solenoid current indicated by an ammeter. The output voltage signal from the induction coil of the micro-fluxgate was analyzed using an oscilloscope, to which it was directly connected.

Figure: Schematic Block Diagram of the Fluxgate Testing System

During magnetic sensor testing, interference from external magnetic fields, particularly the Earth's magnetic field, must be eliminated. The Earth's magnetic field consists of the main static field, which is relatively stable, and varying weaker transient components. Ensuring a stable ambient magnetic environment is critical for accurate measurements. An ideal environment is a zero-magnetic space (where magnetic field intensity remains 0 nT). Given that the Earth's magnetic field strength ranges from approximately 50–60 μT and can significantly interfere with fluxgate testing, magnetic shielding devices are often employed in practical tests to simulate a zero-magnetic environment.

Experimental Results:

(1) Influence of Excitation Current on Sensitivity and Linear Range:
To test the impact of different excitation currents on the sensitivity and linear range of the micro-fluxgate, a fixed-frequency sinusoidal excitation of 500 kHz was applied, with excitation current root-mean-square (RMS) values of 60 mA, 70 mA, 80 mA, 100 mA, and 120 mA. By varying the external magnetic field, the relationship between the second harmonic amplitude of the output voltage and the external magnetic field under these excitation currents was measured, as shown in the figure below.

Figure: Variation Curves of Second Harmonic Amplitude with External Magnetic Field Under Different Excitation Currents

(2) Influence of Excitation Frequency on Sensitivity and Linear Range:
To test the impact of excitation frequency on the sensitivity and linear range of the micro-fluxgate, a sinusoidal excitation current of 80 mA was used, with excitation frequencies of 400 kHz, 600 kHz, 800 kHz, 1,000 kHz, and 1,200 kHz. By varying the external magnetic field, the relationship between the second harmonic amplitude of the output voltage and the external magnetic field at these excitation frequencies was measured, as shown in the figure below.

Figure: Variation Curves of Second Harmonic Amplitude with External Magnetic Field Under Different Excitation Frequencies

During the testing of the fluxgate, as the excitation frequency increases, the eddy current effect and skin effect in the iron core intensify, leading to significant energy losses and affecting the performance metrics and operational effectiveness of the fluxgate. Additionally, the amplitude-frequency characteristics of the output circuit undergo noticeable changes with increasing excitation frequency. Consequently, the benefits of increasing frequency on improving fluxgate performance gradually diminish.

Figure: ATA-4011C High-Voltage Power Amplifier Specifications and Parameters