Battery Voltage Sensor Saved

This circuit conditions a battery voltage for a voltage control loop and also for computer sampling. The signal is first attenuated and filtered with a difference amplifier. A difference amplifier is used to eliminate possible errors associated with an imperfect ground. The second filter is a two-pole active filter set at the same corner frequency as the difference amp. A third passive filter provides further scaling and filtering. At the 100 Hz corner frequency, the circuit provides 9 dB of attenuation. Two active-low logic signals give an indication of a over voltage (>15 V), or under voltage (<10 V) condition.