A current detecting system based on resistance sampling method is designed. The voltage following structure is designed between the current detecting circuit and the A/D circuit eliminates disturbance effect from A/D circuit to current detecting process. Source of errors in current detecting are systematically analyzed

theoretical analysis shows that the system errors are caused by sampling resistor

offset voltage of operational amplifier and offset error of ADC VM

and offset voltage

among them

Vos is the main source of errors. Test results show that

the proposed current detecting circuit can achieve real-time detection of current

the detection precision of current is 10 μA

and the measurement error rate is lower than 5 %.