Keysight technologies u1583b current clamp keysight technologies u1583b the keysight technologies u1583b is a dual range ac current clamp which enables you to take current readings without breaking the circuit being measured its 40a and 400a dual range gives you the flexibility you need in a single instrument suitable for measuring dc and ac currents up to 400a the u1583b can be connected to a handheld digital multimeter or handheld oscilloscope via a bnc adaptor keysight technologies u158