用与门实现差频测量

Research on differential frequency measurement using AND gate

石英晶体压力温度传感器被广泛应用在一些要求高精度、高分辨率的场合,其原理为将可变晶体和基准晶体构成的振荡电路的频率输出进行差频得到信号输出。输出信号带有一定的基本频率,要实现高精度测量,应减去基本频率信号再进行频率的测量,带来的问题是求两频率的差。本文从理论上严格证明了用与门实现差频测量的可行性,并定量地给出了这种方法的适用条件;同时用Max274芯片设计了8阶切比雪夫低通滤波电路。实验证明,在一定条件下用与门附加滤波电路实现差频测量是完全可行的。

Quartz pressure sensor is widely used in many fields that require high precision, long-term stability, rugged ness, and rapid transient response. The quartz sensing elements provide high stability and extremely fine resolution for pressure measurement, But its output signal frequency includes elementary frequency. The problem of measurement precision should be solved to eliminate the elementary frequency from output signal frequency. The feasibility of differential frequency measurement using AND-gate is proved theoretically. The application conditions of this method are also given. At the same time, 8th-order Chebyshev low-pass filter circuit using Max274 is presented, Experiments prove that it is feasible to make differential frequency measurement using AND-gate and additional filter circuit.