Resonant frequency detection and adjustment method for a capacitive transducer with differential transformer bridge

REVIEW OF SCIENTIFIC INSTRUMENTS 85, 055001 (2014)

M. Hu, Y. Z. Bai,a) Z. B. Zhou,b) Z. X. Li, and J. Luo
MOE Key Laboratory of Fundamental Physical Quantities Measurement, School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China
(Received 23 February 2014; accepted 14 April 2014; published online 2 May 2014)

The capacitive transducer with differential transformer bridge is widely used in ultra-sensitive space accelerometers due to their simple structure and high resolution. In this paper, the front-end electronics of an inductive-capacitive resonant bridge transducer is analyzed. The analysis result shows that the performance of this transducer depends upon the case that the AC pumping frequency operates at the resonance point of the inductive-capacitive bridge. The effect of possible mismatch between the AC pumping frequency and the actual resonant frequency is discussed, and the theoretical analysis indicates that the output voltage noise of the front-end electronics will deteriorate by a factor of about 3 due to either a 5% variation of the AC pumping frequency or a 10% variation of the tuning capacitance. A pre-scanning method to determine the actual resonant frequency is proposed followed by the adjustment of the operating frequency or the change of the tuning capacitance in order to maintain expected high resolution level. An experiment to verify the mismatching effect and the adjustment method is provided. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4873334]