Instrument current transformers (CTs) are widely used in various types of electrical energy measurement. Eddy current losses, losses of hysteresis, a saturation of CT, and inevitable flux leaks could lead to errors including errors in the ratio and phase angle. Improving the accuracy of CT measurement could be achieved in many ways. In this study, a bisection calibration method to overcome the error by implementing correction factor integrated with the Arduino codes is investigated. The reliability of this system has been tested in two different situations, which are a constant and variable load experiments. The result shows that the readout of the developed instrument using 100 A/50mA CT could achieve the deviation value of less than 2%, confirming the excellence accuracy of energy meter.