电容式涡街流量传感器的环形转换电路研究

Study on the Loop-Diodes Signal Transform Circuit of Vortex Flow Transducer with Differential Capacitances Sensor

探讨了差动电容环形转换电路的机理,指出输入信号的不平衡将导致一个新的平衡过程,在最终的稳定状态中,流过跨接电容两端的充放电电荷始终趋于动态地保持相同.根据这一理论建立起一个关于输入输出的通用方程,并得到实验数据的支持.由方程导出其电压输出的简洁公式,用以定量分析电容式涡街传感器的信号转换过程,这对于优化电路设计具有重要指导意义.分析表明,涡街的环形电路输出信号只是在输入的高频载波上迭加了一个幅度正比于激励的低频交变信号;高品质振荡电路能有效提高信噪比,而最简便的方法是利用MCU晶振产生的信号直接作为环形电路的激励,在保证激励信号的幅度的基础上,电源电压降低到原来的1/2;激励源电流降低了一个数量级,同时具有稳定性,这对于变送器的智能化和微功耗化的实现起到关键作用.

The mechanism about loop-diodes signal conversion circuit of differential capacitance is probed into deeply ,it shows that when the input signal lose its balance ,it inevitably leads to a new process for equilibrium,the two quantities of electric charge and discharge through the capacitances contacted the two output terminals tend to maintain equal dynamically. In the light of this idea, a general equation that unites the input excitation and output was introduced and supported with a serious experiment data. A simplify formula was deduced consequently and used to analyse the output quantitatively for the signal transformation process of the differential capacitances vortex flow transducer. It benefits largely to the optimization of circuit design instructively. The result shows that the output of vortex convert circuit is consisted of a high frequency input excitation carried a wave modulated by a low frequency vibration signal. Meanwhile the latter＇s amplitude is proportional to the former＇s ; higher quality oscillation circuit raises largely the ratio of signal to noise , as a well shortcut,MCU＇s oscillation signal can also provide a excitation directly, on the basis of higher excitation amplitude, the power voltage of the oscillation source cut down by a half original ,the current lowered by a tenth and keeps stable , this acts as a key to the realization of intelligent transducer that features micro-dissipation adapted battery supply or transmission with two wires mode.