Design and test of LC wireless passive strain sensor integrated with ferrite

To solve the problem of electromagnetic signal transmission failure caused by LC wireless passive strain sensor in metal environment, ferrite material is integrated on the back of the sensor. The principle is to realize electromagnetic signal coupling test in metal environment by suppressing induced electromotive force generated by eddy current effect of electromagnetic wave on metal surface. Through simulation verification of HFSS software, LC wireless passive sensor signal failure in metal environment. After adding ferrite to the back of sensor base, it is concluded that ferrite can realize electromagnetic signal transmission of LC sensor in metal environment through frequency sweep. The optimum thickness of ferrite is 0.32 mm. The test platform of equal strength cantilever beam was built. The results show that LC sensor can resist metal environment interference through ferrite in metal environment. When the frequency is 37.7 MHz, LC wireless passive test system can realize signal transmission well, and the corresponding S_11 value is −25.6 dB. The sensitivity of the sensor is 61.54 Hz/με in the strain range from 0 to 1300 με. The test results show that ferrite is beneficial to realize the strain measurement of LC wireless passive sensor in metal environment.