Measurement errors are obtained by comparing each of the measured current data with the standard current data. We repeated the experiments three times and the measurement errors of the worst experiment results are shown in Fig. 5. Fig. 5(a) and (b) indicates the measurement errors of increasing current and decreasing current respectively. From Fig. 5, it is shown that the measurement errors are within the range of ±5.5 mA and the corresponding accuracy is within 1% at the current measurement range from -300 mA to 300 mA.