对于直流电流测量﹐在电流通道串联一电流分流器﹐将电流转换成直流电压信号。
For DC current measurement, a current shunt is place in series in the current path and convert the current to a DC voltage signal.
同时，设计了用于牵引逆变器控制的二次数字陷波器以及低通滤波器滤除直流电压信号的二次脉动。
Simultaneously, the second order notch filter and low-pass filter are designed to filter the second order rippled DC voltage signal.
为了给智能仪表提供廉价标准电流信号输出接口，可以使用RC低通滤波器，从PWM中分离出与占空比成正比的线性直流电压信号。
To provide intelligent instruments with the cheap interface of the standard current sign, the RC low pass filter is used for producing a voltage signal which is proportion to PWM's duty rate from PWM.
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