The origin of this coefficient is also discussed. The results indicate that the selleck kinase inhibitor conventional usage of SWF shift as a measurement of gas concentration is not appropriate, as the SWF shift is not identical to MRF shift. Instead, SWF shift measured should be revised by a coefficient to approach the MRF shift. The further discussion in this work also proves that this finding can be applied to all the sensing system using an actuating-detecting oscillator loop.2.?Experimental Details2.1. Brief Description of the SAD Circuit LoopWith a presumption of small deformation, an electrical model of a piezoelectric micro-cantilever is developed [3].The mechanical function analogy of the electrical components is presented in Equation (1).
Where meffect is the effective mass of the micro-cantilever, k is the spring constant, c0 is the static capacitance of the piezoelectric Inhibitors,Modulators,Libraries layer, �� is the damping coefficient. The k1, k2 are proportionality constants:{C1=k1k2L1=meffectkk1k2R1=2��kmeffectkk1k2C0=c0?k1k2(1)Therefore, the electrical components in the model can be determined by the mechanical properties of the beam, among which C1 and C0 can be seen as a constant, R1 and L1 will vary with the frequencies. Furthermore, the impedance of the micro-cantilever can be determined, as shown in Figure 2. As the impedance of C0 is much smaller than that of C1-R1-L1 branch, the impedance of the micro-cantilever is rather determined by that of C0, and has only a local minimum at the MRF f0. This means the micro-cantilever does not have a good capability of selecting the resonance frequency.Figure 2.
Impedance of the piezoelectric micro-cantilever.Therefore, for ameliorating the frequency selection performance of the beam, a frequency selection network module is designed. The constant capacitor C0 in the electrical model was compensated by Inhibitors,Modulators,Libraries an external tunable capacitor. In an ideal situation, the output of the network should perform as a band-pass filter, having maximum amplitude at the mechanical resonance frequency (see Figure 3).Figure 3.Frequency selection network module.Figure 4 shows the block diagram of the SAD circuit loop. The micro-cantilever Inhibitors,Modulators,Libraries is integrated in the module of frequency selection network, which constitutes the frequency determining unit of the oscillator circuit, and serves like a band-pass filter with a central frequency equal to f0.
The output signal of the frequency selection network is amplified and then adjusted by the following Inhibitors,Modulators,Libraries phase compensator. Batimastat An amplitude limiting Abiraterone CB-7598 module is used to control the amplitude of the signal. Finally, as in reality the output of frequency selection network cannot be reduced to zero at frequencies far away from f0, a band-pass filter is needed, to reduce the secondary mode oscillation of the beam.Figure 4.Schematic illustration of a SAD circuit.