Property of Butterworth Type Low-Pass Filter Used in Lock-in Amplifier for Precise Capacitance Transducer
Based on the fact that Op Amps of Butterworth low-pass filter is non-ideal, the transfer function of VCVS type two-order Butterworth LPF based on non-ideal Amps is deduced theoretically. The influence of non-ideal characteristic on filter is studied, and the relationship between step response and control time of filter based on non-ideal Amps and periphery circuit parameters is analyzed and calculated. The effect of LPF with non-ideal Amps on real-time of tiltmeter is evaluated. The control time and cutoff frequency of LPF are tested by experiment and the results are basically in accord with the theoretical ones.
This work was supported by the National Nature Science Foundation of China under Grant Nos. 61004130 and the Fundamental Research Funds for the Central Universities under Grant Nos. HUECFL20111107.
- 1.Huang Y, Wu LH (2007) Crustal tilt measurement with two-dimension vertical pendulum tiltmeter. Chin J Scientific Instrum 28(8):1514–1517Google Scholar
- 2.Martínez O, Carvajal MA, Morales DP et al (2008) Development of an electrical capacitance tomography system using four rotating electrodes. Sens Actuators A 148:366–375Google Scholar
- 4.Trevor Y, Sun LL, Chris G et al (2004) Silicon-based miniature sensor for electrical tomography. Sens Actuators A 110:213–218Google Scholar
- 6.Cui ZQ, Wang HQ (2010) Improvements on real-time performance of electrical capacitance tomography. Chin J Scientific Instrum 31(9):1939–1945Google Scholar
- 10.Zhu XM, Wang HQ, Zhang LF (2004) The effect of low-pass filter on the real-time performance of ECT system. Chin J Scientific Instrum 25(6):816–819Google Scholar
- 11.Wang HQ, Cao Z (2005) Optimization of low pass filter design in lock-in amplifier. Chin J Scientific Instrum 26(7):684–688; 704Google Scholar
- 13.Huang Y (2008) Experimental study and analysis on noise of mini-displacement capacitance sensor circuit. Chin J Sens Actuators 21(10):1713–1716Google Scholar