The Design And Implementation Of The Low Frequency Accelerometer Calibration System Based On The Gravity Field Method

Due to the specialty of low frequency,large amplitude of vibration and great destructive force of low frequency vibration,low frequency accelerometers are often used to detect the vibration less than 0.1 Hz in large engineering structures such as bridge dams and high-rise buildings.In order to ensure the accuracy and validity of the measurement signal,the low frequency accelerometers are sent to the statutory metrology agency for periodic calibration.When the calibration frequency is lower than 0.1 Hz,the low-frequency calibration device based on vibration table has a small amplitude of the output vibration excitation signal result in the small output voltage of the accelerometer whose low signal-to-noise ratio greatly reduced the calibration accuracy.The gravity field method can apply the 1g peak value of the excitation signal on the accelerometer at very low frequency,which effectively solves the problem above.The gravity field method was used abroad to calibrate the sensitivity amplitude of the low-frequency accelerometer,but the phase cannot be calibrated,and the method has not yet formed as a standard calibration specification.This paper designed and set up the low frequency vibration calibration system based on gravity field method to calibrate the amplitude and phase of the low frequency accelerometers'sensitivity.The main contents of this paper include:1.The design scheme of the calibration system was proposed,the devices were selected and system was built based on the foreign gravity field method calibration device.2.Turntable control model was established,the parameters of the PID controller of each control loop were simulated and tuned based on Simulink.3.The gravity field orientation device was built based on machine vision to measure the initial angle between the direction of the gravity field and the sensitive axis of the accelerometer.4.The calibration system software platform was designed and developed.And calibration system was used to calibrate the amplitude and phase of the low frequency accelerometer's sensitivity.The low-frequency vibration calibration device based on the gravity field method designed by this paper can realize the automatic calibration of low-frequency accelerometer.The calibration results at very low frequency were obviously better than the results based on laser interferometry.And the calibration of the amplitude and phase of the accelerometers' sensitivity can be realized by the calibration system.