Tightly coupled precision sourcing and measurement The 2400 Series SourceMeter Source Measure Unit (SMU) Instruments are the industry’s original line of single-channel voltage/current sourcing and measurement instruments. Each Series 2400 SMU instrument tightly couples a highly stable DC power source and a true instrument-grade 6½-digit multimeter ranging from 1100V to 100nV and 10.5A pulse to 1pA.