LORENTZ KUVVETİ TABANLI, TINLAYAN ve TİTREŞİM GENLİĞİ ÖLÇÜMÜ İLE ÇALIŞAN BİR MEMS MANYETOMETRE

Bu çalışmada titreşim genliği ölçümü ile çalışan Lorentz kuvveti tabanlı ve algılayıcısı tınlaşan MEMS yük hücresi olan bir manyetometre sunulmaktadır. Manyetometre, tarak elektrotlara sahip Çift Bağlı Diyapazon (ÇBD) bir tınlatıcı ile, uçlarından ve ortalarından birbirlerine bağlanmış kirişlerden oluşan bir ızgara yapısından oluşmaktadır. Izgara yapısı, üzerinden geçen akımla Lorentz kuvvetini oluştururken, elektriksel direncin ve yapının sıcaklığının yükselmesini engellemektedir. Maksimum hassasiyet için yapının genlik frekans tepkisinin eğiminin en büyük olduğu tahrik frekansı seçilmiştir. Manyetometre standart SOI (Yalıtkan-Üzeri-Silisyum) mikro-işleme teknikleri kullanılarak 35µm yapısal kalınlıkla üretilmiştir. Yapılan frekans tepkisi testinde ÇBD yapısının tınlaşım frekansının 63812,1 Hz ve 0,2 mTorr'daki kalite faktörünün de 5950 olduğu belirlenmiştir. Testler yapıya dik olarak oluşturulan 30mT manyetik alan altında, 100mA ızgara akımı ve 70mV tahrik genliği ile yapılmıştır. Manyetometrenin orantı katsayısı 113.7 mV/T ve duyarlılığı 965 µT/Hz½ olarak ölçülmüştür.

Anahtar Kelimeler:

Manyetometre, ÇBD (Çift Bağlı Diyapazon), MEMS, Lorentz Kuvveti, Genlik Ölçüm

A Resonant MEMS Lorentz Force Based Magnetometer with Amplitude Detection

This study presents a Lorentz force magnetometer based on vibration amplitude detection with a resonant MEMS load cell structure as a sensor. Magnetometer is composed of a DETF (Double-Ended Tuning Fork) resonator with comb type electrode and a grill structure formed by beams connected from their centers end ends. The grill structure reduces electrical resistance and prevents overheating while generating the Lorentz force. For maximum sensitivity, the maxima of the slope of the magnitude response is chosen for excitation frequency. The proposed sensor is fabricated using a standard SOI micromachining processes with a device layer thickness of 35 μm. The resonance frequency of the DETF is measured to be 63812,1 Hz, Q-factor of 5950 at around 0.2 mTorr ambient pressure. Tests are done for 30 mT magnetic field normal to the resonator plane, with the grill current of 100 mA and excitation amplitude of 70mV. The scale factor of the magnetometer is measured to be 113.7 mV/T with a resolution of 965 µT/Hz½.

Keywords:

Magnetometer, DETF, MEMS, Lorentz Force, Amplitude Detection,

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