Performance measurements of an inertial sensor with a two-stage controlled torsion pendulum

Abstract

A novel two-stage electrostatically controlled torsion pendulum has been developed to simultaneously investigate the performance of a translational and a rotational degree of freedom of an electrostatic inertial sensor on ground. The motions of the proof mass (PM) relative to the electrode frame are monitored by a high-precision capacitance transducer, and are synchronously controlled by electrostatic actuators. The parasitic stiffness induced by capacitance transducers and the effect of the magnetic field are measured. Both translational and rotational motions of the PM succeed to be simultaneously controlled, and the cross-coupling effect between both controlled degrees of freedom is also preliminary measured. The experiments show that the scheme obviously suppresses the translational to rotational effect of the PM, and then effectively improves the torque resolution compared with the single-stage torsion pendulum. The noise floors of the controlled torsion pendulum come to 1.2 × 10−11 N Hz−1/2 along the translational degree of freedom, and 1.4 × 10−13 N m Hz−1/2 along the rotational degree of freedom, near 30 mHz, which are mainly limited by the back action of the capacitance transducer below 0.1 Hz and by the horizontal seismic noise disturbance above 0.1 Hz.

Measurements of temporal and spatial variation of surface potential using a torsion pendulum and a scanning conducting probe

“…Four identical electrodes with an area of 20 × 20 mm 2 , combined with the middle part of the pendulum, act as a differential capacitive transducer to monitor and control the torsional motion of the pendulum [17], by which the gaps between the pendulum and the electrodes are set to be about 680 μm. A dc bias voltage V b and a 50 kHz pumping voltage V p are applied to the middle part of the test mass by the suspension fiber in order to linearize the electrostatic actuator and to drive the capacitive transducer.…”

Three-Dimensional Optical Measurement with Spectroscopic Function Using Fiber Laser Supercontinuum

“…The chamber is continuously driven by the seismic noise, which disturbs the pendulum or balance, and thus limits the experimental resolution to a certain level. A simplified model, as shown in figure 1, is used to conveniently analyse the disturbances contributing to the horizontal seismic noise [8,9,12]. A balance bar and a PM are suspended by two fibres.…”

“…A two-stage electrostatically controlled torsion pendulum has been constructed in our cave laboratory to investigate the performance of the inertial sensor on ground, which is introduced in detail in [12]. The local seismic noise spectrum of the vacuum chamber platform was measured with a triaxial broadband seismometer (CMG-3T, Güralp Systems with the measurement frequency band from 3 mHz to 50 Hz), as shown by a solid line in figure 4.…”

“…In our laboratory, a two-stage electrostatically controlled torsion pendulum has been constructed to investigate the disturbances of the inertial sensor [12]. The PM is electrostatically controlled to keep it motionless with respect to the electrode frame of the inertial sensor.…”

“…The feedback voltages associated with the calibrated sensitivity coefficients indicate the variations of residual forces and torques acting on the PM. The operational principle is introduced in detail in [12][13][14][15].…”