Wireless Strain Measurement with a Micromachined Magnetoelastic Resonator Using Ringdown Frequency Locking

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Resonant magnetoelastic devices are crucial for anti-theft tags and sensing.
• Current detection methods struggle with weak signals and high frequencies in micromachined devices.
• Interrogating stimulus feedthrough to detectors is a significant challenge.

Purpose of the Study:

• To introduce a novel frequency-lock approach for interrogating wireless magnetoelastic strain sensors.
• To overcome limitations of existing detection methods for micromachined devices.
• To enable precise and real-time tracking of sensor resonant frequencies.

Main Methods:

• Utilized a frequency-lock loop with data acquisition hardware and custom software.
• Analyzed sensor ring-down following a brief excitation pulse.
• Implemented a feedback loop to match excitation and resonant frequencies.

Main Results:

• Achieved temporal isolation of the interrogating stimulus from the sensor response.
• Demonstrated near real-time tracking of resonant frequencies for sensors from 120 to 240 kHz.
• Measured strain levels up to 3.5 mstrain with sensitivities up to 14300 ppm/mstrain and response times < 0.5 s.
• Maintained a standard deviation of the locked frequency not exceeding 0.1%.

Conclusions:

• The frequency-lock method effectively interrogates wireless magnetoelastic strain sensors.
• This technique offers significant advantages in signal isolation and frequency tracking.
• The developed method shows promise for advanced sensing applications and improved anti-theft tag technology.