The Instek GCP-300 is designed to measure AC and DC current. The test frequency range of GCP-300 is from DC to 300 kHz. The current measurement range of GCP-300 is from 50mA to 200A. (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.