Non-contact EMAT (Electromagnetic Acoustic Transducer) detection method and system for micro-mass sensor

Abstract

The invention provides a non-contact EMAT (Electromagnetic Acoustic Transducer) detection method and system for a micro-mass sensor. According to the invention, an electrostatic magnetic field is generated by magnets, sinusoidal alternating current is introduced into an excitation coil, a resonance piece is placed above the excitation coil, and resonance is generated when the frequency of the excitation coil is the same as the intrinsic frequency of the resonance piece, so that a secondary alternating magnetic field is induced, and in induction current is generated in a differential detectioncoil; and when a minute amount of substance to be measured is adsorbed to a sensitive thin layer covered on the upper surface of the resonance piece, the resonant frequency of the resonance piece drifts, and the substance to be measured is quantitatively measured through calculating the drifting amount of the resonant frequency. The EMAT is introduced, the acoustic vibration is excited and detected by using electromagnetic induction so as to realize a non-contact scheme, complex structures such as a micro-cantilever beam structure are replaced by the simple structure, and the absolute frequency shift is replaced by the relative frequency difference between different modes, thereby reducing disturbance caused by the external environment, and realizing high-precision measurement for the micro-mass substance.

Description

technical field [0001] The invention relates to the field of micromass sensors, in particular to a non-contact EMAT detection method and system for micromass sensors. Background technique [0002] At present, micromass sensors are a type of mass-frequency sensor that uses the piezoelectric effect of piezoelectric crystals to excite sound waves or vibrations. The three types of high-precision micromass sensor structures that are widely used are quartz microbalances, microcantilever beams, and surface acoustic waves. Quartz microbalances and surface acoustic waves require piezoelectric crystals, which makes the cost of using chips in large quantities relatively high. The mechanism of the micro-cantilever beam is complicated and the manufacturing process is difficult. It is transformed into acoustic vibration, because the excitation and detection system inevitably needs to be in contact with the sensor chip, and it is difficult to achieve non-contact measurement. [0003] Elec...

AI Technical Summary

Problems solved by technology

[0006] At present, EMAT is widely used to excite sound waves, basically for non-destructive testing of metal pipes, aircraft engines, etc., and there is no application of high-precision mass load sensors. This is because the excitation signal is an impact signal. Larger interference, the change of acoustic vibration caused by the mass load is weak and difficult to detect; and the characteristics of the chip itself will drift with the change of the environment, it is difficult to achieve high-precision measurement of the frequency change caused by the adsorption of the object to be measured

Images