应用于硅微机械谐振式传感器的频率计

A Frequency Meter Applied to the Silicon Micro-resonant Sensor

针对硅微谐振式传感器频率测量中精度低的弊端,依据周期测频法原理,设计了一种基于FPGA的测频周期自调整频率计;首先在一个待测信号周期内,对标准信号的上升沿进行计数,粗略计算出待测信号频率和周期;据此对标准信号的上升沿重新计数,从而精确测量出待测信号的频率;测量后的频率信号经过RS-232串行通信接口送入PC上位机,可以实现频率数值的实时显示和储存;测试表明:采用该频率计测量1Hz^2 MHz方波信号的相对误差可以达到10-7量级;利用该频率计测量谐振式传感器闭环自激测量电路输出的谐振频率信号,频率信号稳定在1Hz以内。

Due to the disadvantage of low precision in frequency measurement for the silicon micro-resonant sensor,a frequency meter based on field-programmable gate array（FPGA）is designed according to the principle of periodic frequency measurement.The rising edge of the standard signal is counted in a signal period to be measured,the frequency and period of the signal to be measured are roughly calculated.According to this,the rising edge of the standard signal is re-counted so that the frequency of the signal to be measured can be accurately measured.The measured frequency signal is sent to PC through RS-232,and the frequency value can be displayed and stored in real time.The experimental result shows that the relative error of 1 Hz to 2 MHz square wave signal measured with this frequency meter can reach the magnitude of 10-7.The frequency meter is used to measure the resonant frequency output from the closed-loop self-excited measuring circuit of the resonant sensor.The frequency signal is stable within 1 Hz.