The key of density measurement of resonant density sensor is the measurement of resonant frequency.The existing resonant frequency measurement methods,such as frequency measurement method,period measurement method and FFT method,have limited their accuracy due to noise,pulse error and other factors.In order to solve the problem,a resonant frequency measurement system based on phase-locked amplifier is designed,and the detection circuit converts the measurement of alternating vibration signal into that of DC constant voltage.The linear relationship between DC voltage and excitation frequency is found in the resonant region and utilized to present and realize an algorithm based on scan frequency to measure the resonant frequency automatically.The density calibration ex-periment is carried out at(20±0.05)℃,and the temperature compensation of the density sensor is carried out.The experimental results show that in the measurement range of density from 700 kg/m3 to 1 000 kg/m3,the stability of the resonant frequency measured can reach 0.002%,the maximum density error measured by the sensor is 0.48 kg/m3,and the maximum comprehensive measurement error is 0.069%,which verifies the effectiveness and accuracy of the resonant frequency measurement method.
关键词
谐振式密度传感器/谐振频率/锁相放大/温度补偿/检测电路
Key words
resonant density sensor/resonant frequency/phase-locked amplification/temperature compensation/testing circuit
维普
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