| As a mass flowmeter that directly measures the quality of fluids,Coriolis mass flowmeter is widely used in fields such as precise material proportioning,fuel consumption control,and trade and economic settlement.As the core component of the Coriolis mass flowmeter,the drive system maintains the steady-amplitude vibration of the flow tube by providing and regulating the driving energy,which provides the basis for the accurate measurement of the Coriolis mass flowmeter.Coriolis mass flowmeter based on analog drive system has been mass-produced and widely used in China due to its unique advantages.However,in practical applications,this kind of Coriolis mass flowmeter still has problems.Aimed at the problem of insufficient driving capacity of the analog driving Coriolis mass flowmeter,an analysis method based on the driving characteristic graph was proposed,and the driving characteristics of three kinds of existing analog driving systems were analyzed based on the method,the existing problems and their causes were pointed out,and the basis for further improvement of the analog driving system was provided.According to the analysis results,the single-ended simulation drive system starts slowly,and when measuring gas-liquid two-phase flow,the system has no stable working point,and the flow tube is easy to stop vibration.When the differential simulation driving system is measuring the gas-liquid two-phase flow,the amplitude of the driving signal decreases.The improved single-ended simulation drive system still has limited driving energy when measuring gas-liquid two-phase flow.A new type of differential simulation driving system is proposed.Based on the analysis method of driving characteristic diagram,the feasibility of the system is analyzed,the circuit is designed and realized,and the driving experiment is carried out.The experimental results under gas-liquid two-phase flow show that the driving signal amplitude of the new differential driving system is larger and more stable,and the sensor signal amplitude is larger.Experimental results under single phase flow show that the new differential simulation drive system can accelerate the vibration start speed by flexible amplitude control,and the vibration start time is shortened to 2.3s.The new differential simulation drive system can improve the driving ability of the system effectively.For analog-driven Coriolis mass flowmeters,it is difficult to determine the optimal vibration amplitude,which makes it impossible to give full play to its flow measurement advantages.To solve this problem,a Micro Motion DN25 caliber Ω sensor with excellent performance was used to match the analog drive transmitter。First,the signal under different amplitudes is collected,and the influence of amplitude on the performance of the Coriolis mass flowmeter is analyzed from the perspectives of zero point,amplitude stability,waveform distortion,signal power spectrum,signal-to-noise ratio and system driving efficiency.Then,the calibration experiments of single-phase water flow with different amplitudes are carried out,and the optimal amplitude of the system is determined according to the calibration error and repeatability.The results show that the zero point increases with the increase of amplitude,and the amplitude of 349mV～533mV is more conducive to zero point stability.With the increase of amplitude,the waveform distortion becomes more serious,the high-order harmonic component also increases,and the noise signal power also shows an increasing trend,which affects the SNR and reduces the driving efficiency.However,too small amplitude will aggravate the amplitude fluctuation of the sensor amplification signal and affect the measurement results.In addition,when the amplitude is 439.81m,the calibration experiment error is the smallest,the error curve is the smoothest,and the repeatability meets the requirements.Therefore,the amplitude of Coriolis mass flowmeter should not be too small or too large,the best amplitude is about 439mV. |
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