Abstract
Ultra-sensitive inertial sensors are one of the key components in satellite Earth’s gravity field recovery missions and space gravitational wave detection missions. Low-noise capacitive position transducers are crucial to these missions to achieve the scientific goal. However, in actual engineering applications, the sensor head and electronics unit usually place separately in the satellite platform where a connecting cable is needed. In this paper, we focus on the stray-capacitance influences of coaxial cables which are used to connect the mechanical core and the electronics. Specially, for the capacitive transducer with a differential transformer bridge structure usually used in high-precision space inertial sensors, a connecting method of a coaxial cable between the transformer’s secondary winding and front-end circuit’s preamplifier is proposed to transmit the AC modulated analog voltage signal. The measurement and noise models including the stray-capacitance of the coaxial cable under this configuration is analyzed. A prototype system is set up to investigate the influences of the cables experimentally. Three different types and lengths of coaxial cables are chosen in our experiments to compare their performances. The analysis shows that the stray-capacitance will alter the circuit’s resonant frequency which could be adjusted by additional tuning capacitance, then under the optimal resonant condition, the output voltage noises of the preamplifier are measured and the sensitivity coefficients are also calibrated. Meanwhile, the stray-capacitance of the cables is estimated. Finally, the experimental results show that the noise level of this circuit with the selected cables could all achieve 1–2 × 10−7 pF/Hz1/2 at 0.1 Hz.
Highlights
The high precision inertial sensor is one of the key payloads in satellite Earth’s gravity field recovery missions [1] and space gravitational experiments [2,3,4,5]
Concerning the capacitive position transducer, the mechanical core of the gradiometer in the GOCE mission consists of a low expansion carbon-carbon sandwich panels and six electrostatic accelerometers’ sensor heads [17,18]
In space gravitational detection missions, the gravitational reference sensor system consists of a cubic test mass and surrounding electrodes assembled in a vacuum chamber
Summary
The high precision inertial sensor is one of the key payloads in satellite Earth’s gravity field recovery missions [1] and space gravitational experiments [2,3,4,5]. The capacitive position transducer is crucial to the success of these missions where it measures the relative motion between the test mass (TM) and the electrodes frame. For space gravitational wave detection mission LISA, and in-flight tests have achieved the anticipated. In actual space engineering applications, the sensor head and the electronics are usually two separate equipment in the satellite. Concerning the capacitive position transducer, the mechanical core of the gradiometer in the GOCE mission consists of a low expansion carbon-carbon sandwich panels and six electrostatic accelerometers’ sensor heads [17,18]. The electronics of the gradiometer needs to operate far from the mechanical core in the satellite dimension. In space gravitational detection missions, the gravitational reference sensor system consists of a cubic test mass and surrounding electrodes assembled in a vacuum chamber. The analysis of capacitive sensor noise [19,20,21,22,23]
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