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Characterizing MEMS Magneto-Impedance Sensors Using Agilent 4294A and E4991A Impedance Analyzers Application Note Excellent accuracy and repeatability Easy evaluation of Magneto- Impedance characteristics A wide variety of design-automation tools and functions Figure 1. Agilent 4294A and E4991A Impedance Analyzers Introduction Evaluation of MI Characteristics This application brief describes the benefits of using of the Amorphous Magnetic Agilent impedance analyzers for device characterization of MEMS Magneto-Impedance (MI) sensors and how they Material improve design and test efficiency while offering a wide variety of design-automation tools and functions. Evaluating the MI sensor's sensitivity is very important because its sensitivity depends on the impedance change of the amorphous magnetic material when high frequency Agilent Impedance Analyzers is applied. The 4294A covers the range of 40 Hz to 110 MHz and the Z E4991A, from 1 MHz to 3 GHz. These impedance analyzers (see Figure 1) offer excellent impedance measurement ac- curacy and are optimum tools for both design and manufac- turing test of MEMS MI sensors. MEMS MI Sensor Hex The MI sensor applies the principle of the MI effect. The impedance of the amorphous magnetic material changes 0 depending on the external magnetic field when high Figure 3. Impedance vs. Magnetic Field frequency current is applied. Figure 2 shows the equation of this characteristic. High sensitive MI sensors are easily miniaturized into MEMS devices. For an MI sensor, the impedance is low at low frequen- cies and changes rapidly at high frequencies (Figure 4). The instrument's impedance accuracy with sufficient test a frequency resolution is required to know the true perfor- Z= Rdc (1 + j)