Resolution Test Of Nano-g Accelerometers Based On Mass Attraction

High-precision accelerometers are currently widely used in geophysical sciences,navigation and guidance systems,and underground resource exploration.In order to ensure the accuracy of navigation and resource exploration,the accelerometer needs to be tested.The resolution is an important indicator to measure the performance of the accelerometer,which is a key content in the accelerometer test.With the continuous improvement of accelerometer performance indicators,commonly used resolution detection methods,such as test methods based on equipment such as indexing heads,linear vibration tables,precision centrifuges,etc.,are difficult to achieve ng level resolution detection for changing signals.This article chooses the gravitational calibration method to test the resolution of the accelerometer.Taking a high-precision reed accelerometer developed by this group as an example,it solves two problems in high-resolution testing: the gravitational source moves at a specific frequency,accurately give the accelerometer with a varying acceleration signal of the order of ng;when testing on the ground,suppress the environmental vibration noise and the interference source caused by the movement of the gravitational source.Aiming at the resolution test of high-precision accelerometer,the thesis first investigates and analyzes the commonly used resolution test methods,and selects the gravity calibration method for resolution test.The gravitational source produces a spatial position change at a certain frequency relative to the accelerometer to be measured,thereby generating a gravitational acceleration signal at a certain frequency.The high-precision accelerometer outputs the test signal,which is extracted and compared with the expected theoretical gravitational acceleration signal,to calibrate the resolution of a high-precision accelerometer at a specific frequency.This article specifically addresses the problem that the ng-level acceleration resolution test is susceptible to external noise interference,and proposes a solution that uses two identical high-precision accelerometers in different spatial positions relative to the gravitational source to output the difference to suppress the external common mode interference.Observing the differential effect of the two accelerometers on the gravitational acceleration response,we successfully suppressed the interference of external noise by 1-2 orders of magnitude,and solved the main technical difficulties of ng resolution detection.The test was made with the high-precision accelerometer made by the research group as the object,using a swinging gravitational mass source.We applied a three-axis microseismograph as a reference to accurately measure the sensitive axis posture of the accelerometer through a correlation analysis method,and then eliminated the ground pulsation noise,the vibration caused by the swing of the gravitational source and the ground tilt through the differential method of the output of two identical accelerometers,and overcame the influence of the magnetic field on the test,eliminated the influence of airflow fluctuation noise and other factors.The accelerometer output signal related to the periodic change of the spatial position of the mass source is extracted.The accelerometer can successfully measure the acceleration signal of 1.2 ng at 0.78 Hz,which is consistent with the prediction according to the noise floor of the accelerometer.This result demonstrates the resolving capability of our home-made accelerometer,and feasibility of the proposed method.