新型数字-频率变换在科氏质量流量计中的应用

对新型全数字式科氏质量流量计频率输出信号采用数字—频率转换D/F(Digital to Frequency Conversion)方法实现.利用晶振和现场可编程门阵列FPGA(Field Programmable Gate Arrays)与数字信号运算处理单元DSP(Digital Signal Processing)配合实现频率量输出,有效避免了传统的模拟式科氏质量流量计的电压—频率V/F(Voltage to Frequency Conversion)转换方法中存在的精度不高、温漂以及电路复杂等问题,而且也消除了由于频率刷新造成的输出频率非整周期对输出结果的影响.实验表明,该数字—频率转换方法具有较高的转换精度,实现了输出频率的整周期刷新,不存在V/F转换电路的温漂等问题.该电路简单,与数字电路实现无缝接口,对于数字系统的频率输出设计具有较高的参考价值. 

Application of novel method of digital to frequency conversion in Coriolis mass flowmeter

A new data transforming method of D/F(digital to frequency conversion) was adopted to export frequency in the novel digital Coriolis mass flowermeter.The frequency output was completed by the crystal and the FPGA(field programmable gate arrays) together with the DSP(digital signal processing).The influence of V/F(voltage to frequency conversion method) in the traditional analog Coriolis mass flowmeter was avoided,for example,the conversion precision was not high,temperature excursion and the circuits were more complex.And the frequency output was not whole period because of the frequency update,which influenced the frequency output result.The experimental results show that the transforming method of digital to frequency conversion has high conversion precision and realizes the whole period frequency output.In addition,it also has not the temperature excursion of the voltage to frequency conversion method.The circuits are simple and seamless to connect with digital circuit.Thus the method is well worthy applying in digital system.