GFUVE Q40 AC Current Transformer Clamp, 2 Pack The Q40 ct clamp is an ac current clamp can be used to measure currents up to 500 A when used in... GFUVE AC Current Clamp, 40 mm. The Q40 is an ac current clamp utilizing the magnetic principle. GFUVE Current transformer clamp meters are equipped with rigid jaws of made of ferrite iron. The jaws are individually wrapped by coils of copper wire. Together, they form a magnetic core during measurements. Their basic operation is like that of a transformer. It works with one primary turn, or winding, which in nearly all cases is the conductor . The GFUVE clamp-on current transformer is very popular with our customers due to its fast and easy installation Produced with amorphous silicon core or permalloy core, this product features small size, high precision good stability and good anti-interference This product is widely used for measuring power and energy in the fields of electric power, communication and monitoring system. Besides the high precision and the small phase error this clamp-on current transformer can be used to measure a wide variety of electric parameters without disconnecting the exiting electric system.