Source Measure Units (SMU) or SourceMeter® are an ingenious combination of 4 functions in a single box. Thus, a SourceMeter® contains a voltage source, a current source, a voltmeter and an amperemeter. Everything is designed bipolar and therefore SourceMeters have a true four-quadrant operation. This means, that the instruments have an active source, as well as an active load (sink). The individual models offer voltages from Microvolts to 3kV and currents of a few Femtoamperes to 100A. With this wide U/I ranges, resistance measurements can be realized from μΩ (conductance) to PΩ (isolation). The source- and measurement timing starts from DC level down to 200μs pulse operation.