Feedback control of torsion balance in measurement of gravitational constant G with angular acceleration method
REVIEW OF SCIENTIFIC INSTRUMENTS 85, 014501 (2014)
Li-Di Quan,1,2 Chao Xue,1 Cheng-Gang Shao,1 Shan-Qing Yang,1 Liang-Cheng Tu,1 Yong-Ji Wang,2 and Jun Luo1,a)
1MOE Key Laboratory of Fundamental Physical Quantities Measurements, School of Physics, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People’s Republic of China
2School of Automation, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People’s Republic of China
(Received 11 August 2013; accepted 18 December 2013; published online 10 January 2014)
The performance of the feedback control system is of central importance in the measurement of the Newton’s gravitational constant G with angular acceleration method. In this paper, a PID (Proportion-Integration-Differentiation) feedback loop is discussed in detail. Experimental results show that, with the feedback control activated, the twist angle of the torsion balance is limited to 7.3 × 10−7rad/√Hz at the signal frequency of 2 mHz, which contributes a 0.4 ppm uncertainty to the G value. © 2014 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4861189]
