Design, Fabricaton and Application of a Micro Eddy Current Positioning Sensor

• Main Authors: Su Hsing-Ming, 蘇信銘
• Other Authors: Da-Chen Pang
• Format: Others
• Language: zh-TW
• Published: 1998
• Online Access: http://ndltd.ncl.edu.tw/handle/80679814935146213339

碩士 === 華梵大學 === 機電工程研究所 === 87 === The purpose of this thesis is to design and fabricate a micro eddy current positioning sensor used in the magnetically suspended micromotor. Because of the limited space in the micromotor, the sensor will put in the air gap between the stator and rotor to measure its radial displacement. This thesis discusses the fundamental theory of the eddy current sensor and analyzes the magnetic field to design the photomask of micro coils. In addition, we apply the thick-film photoresist and semiconductor process technology to fabricate the microcoils. Three photomasks are designed to make single or double layer with four different design patterns of the coils. We also build amplitude demodulation(AM) sensor circuit. Various experiments are conducted at different operation frequencies and heights. We find out that the output voltage is both proportional to the oscillating frequency and the target shadowing area in the sensor but inversely proportional to the distance between the target and the sensor. For the single layer coil with both line width and line space of 10 um,the sensitivity can reach to 0.044V/um at 12MHz in the operating range of 400 um. The linearity error is within 1-2um and drift error is limited to 10-15mV for all testing samples. We notice that the modulation/demodulation chip LM1496 contributes most of drift error. If we reduce the amplification after the LM1496 and increase amplification in front of the LM1496, we can improve the accuracy.