Design And Test Of Temperature Control System For High Precision Accelerometers In Gravity Measurement

Accelerometers are the critical sensing component used in precise measurement of the gravity.The overall accuracy and performance of the sensor are inevitably affected by ambient temperature fluctuations,which includes its zero-bias offset and scale factor.Therefore,in order to suppress the adverse effects of temperature fluctuations,it is necessary to employ temperature control systems in such sensor systems.The purpose of this research is to carry out an in-depth study on the key technologies of a precise temperature control system.Based on the temperature control requirements of the accelerometers developed in the research group,a milli-kelvin-level high-precision temperature control system design scheme is proposed in this study.For the implementation of the temperature control system,the selection of key components such as temperature sensors,actuators,and voltage-current converters are discussed in this study.The design of temperature detection circuits,PI control circuits,drive circuits,and voltage stabilizing circuits to reduce temperature interference to accelerometer testing are also designed and implemented.This work will help further increase gravity measurement accuracy.In this study,the design of a small volume,high-precision analog temperature controller is described in detail.For high precision,thermistor type temperature sensor,analog PI(Proportional Integral)control circuitry,and polyimide electric heating film type temperature control heating element are used.The signal amplifier is constructed using INA 330 to amplify the temperature error signal.Subsequently,the amplified error signal is transmitted to a precision analog PI compensation network,and the control signal is brought to the level suitable for driving the power MOS(Metal-Oxide-Semiconductor)tube,then change the working state of the polyimide electric heating film.Eventually,the precise control of the temperature is achieved.To adjust the analog PI parameters,this study also utilizes a method of PI parameter adjustment approach,based on the transfer function obtained using a lock-in amplifier.The parameters are then placed in the MATLAB’s System Identification Toolbox and Simulink simulation plug-in,and ultimately the PI parameters can be tuned accordingly.The approach is verified through simulations and subsequent testing.The experimental results show that,when the outer temperature is maintaining a 40℃ ambient temperature,the inner temperature controller can maintain the system at 80 ℃.And the temperature fluctuation of the temperature control system designed in this study can achieve a peak-peak temperature stability of ±118 μK,with a standard deviation of 27μK,within 10h of operation.The long-term stability is also characterized,and the peak-peak temperature fluctuation is 0.5 mK,with a standard deviation of 63 μK with 120h of operation.Potentially,this study can be beneficial for future development of gravimeters and gradiometers.