Direct Current Sensor

The input to this circuit is a current that is proportional to a greater current measured by a current transducer. The signal is first filtered and converted to a voltage with a resistor and capacitor. The next circuit is a second order Sallen Key filter with Butterworth damping. The signal is then filtered and further scaled with another single-pole filter and voltage divider. All together the conditioning circuit has four poles. Each filter is set with a corner frequency of 1000 Hz. The gain is -9dB at the corner frequency. The circuit also includes an active low over current indicator.