说明：  推荐一份"555 集成电路用于测量电压的电路",摘录了 555 电路进行高精度低成本测量电压的单元电路.主要通过 VCO(压控振荡器) 和 VFC (电压频率转换器)方法....
(555 is a cheap and widely used circuit, where a special extract of 555 by VCO (voltage controlled oscillator) and VFC (voltage-frequency converter) for low-cost high-precision measurement of the voltage circuit unit 555 for-----" measuring the voltage of the circuit " in the voltage measurement method, the corresponding output voltage signal to the input frequency, for reference!)