Sometimes it's the basics that reveal what you really need to know. When testing for fundamental characteristics of components and materials, you often need to source a precise 2- or 4-quadrant voltage (or current) and read the corresponding current (or voltage). What could be more basic? And what's the big deal? You can use a voltage or current source and a separate precision meter, end of story.
Or maybe not. It turns out that properly coordinating and controlling the instruments, their test setup, and the sourcing and resultant data can become a "multiple-hand" juggling operation, resulting in time-consuming test with inconsistent or questionable results. (Note: that's why "curve tracers" are needed for basic component test.)
That's where a source/measure unit comes in. An SMU is a four-quadrant supply plus a digital multimeter: it combines the basic source and meter, but also integrates the actions of both, including basic ramping up/down, or with more complex waveshapes, and does it at higher current and voltages, and even 4-qudrants (depending on the unit).
Typical SMU applications include testing of semiconductors (2- and 3-terminal), photovoltaic cells, batteries, new material, and passive components (even resistors have their "issues").
The B2900A series of SMU from Agilent Technologies Inc—their first benchtop entry into this market—drives ±210V with current ranges of ±3A DC and ±10.5A pulsed mode operation (within a specified envelope). But it is not just a high-power/high-current SMU: it can resolve down to 100 nV and 10 fA, at up to 15,000 measurements/sec, showing up to 6 ½ digits. It combines the sourcing/measurement functions with built-in standard waveform generation, so you can test with designed drive functions, or you can load the SMU with your waveform and use it as an arbitrary waveform generator (AWG). The SMU digitizes in 10 microseconds, making it suitable for transient events.
But an instrument with solid technical attributes is only part of what SMU users need. To enhance ease of use in setup, basic readout, analysis, and more, the B2900A series has a 4.3" color display for both graphical and numerical views on setup and results. The GUI , in conjunction with the SMU's front-panel buttons, lets you set up and initiate tests and operating cycles; it also lets you see your test data in "plain" numerical format, as well as common graphs and even a rolling time-display chart mode. Or, if you are not there in person, or you are building up a test system, you can communicate with the instrument via Ethernet, USB, and even a venerable IEEE-488 GPIB port.
Models, availability, and price: The B2901A is a one-channel, 100-fA resolution unit; the B2902A is a two-channel, 100 fA unit; the B2911 is one channel, 10 fA; and the B2912A is two channels and 10 fA. All versions are available now, with pricing starting at $$5671.
For more information: go to Agilent at http://www.agilent.com/find/B2900A. You can also check out a "background" document on SMUs at http://www.agilent.com/about/newsroom/tmnews/background/B2900ASMU/.