The Instek GCP-500 is designed to measure AC and DC current. The test frequency range of GCP-500 is from DC to 500 kHz. The current measurement range of GCP-500 is from 30mA to 150A. (Do not clamp the probe onto circuits with voltages greater than 600 VAC.) The current probe is equipped with an AC power converter and designed to give priority to the external power supply. If there is no 9V alkaline battery or the power is insufficient, the AC power converter can be used to provide power so that the measurement will not affected.