The active filter acts as an infinite impedance to the external for the fundamental frequency and as a low resistor for harmonic frequencies.
对外电路而言，在基波频率下有源滤波器被控制为无限大阻抗，在谐波频率下被控制为小电阻。
2
For hardware design, RC filter, voltage sensitive resistor and photoelectric isolation method are used to eliminate interference signal in sampling channel and A/D channel.
在硬件方面，采用RC滤波器、压敏电阻、光电隔离等措施，消除了采样通道及A/D通道的干扰信号；
3
The input and output of the ceramic filter are tied together. The filter's center terminal (normally grounded) is connected to the current limiting resistor.