Keithley - Choosing the Optimal Source Measurement Unit Instrument for Your Test and Measurement Application

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By Mark A. Cejer, Marketing Director and Lishan Weng, Applications Engineer, Keithley Instruments, Inc.

Stated in the simplest possible terms, a source measurement unit (SMU) instrument integrates the capabilities of a precision power supply (PPS) with those of a high-performance digital multimeter (DMM) in a single instrument. For example, SMU instruments can simultaneously source or sink voltage while measuring current, and source or sink current while measuring voltage (Figure 1). They can be used as stand-alone constant voltage or constant current sources, as standalone voltmeters, ammeters, and ohmmeters, and as precision electronic loads. Their high performance architecture also allows using them as pulse generators, as waveform generators, and as automated currentvoltage (I-V) characterization systems.

The real benefit of SMU instruments for test and measurement applications comes from their ability to source and measure signals simultaneously. When compared with using separate instruments to handle each function, SMUs’ simultaneous operation provides for faster test times, simplified connections, improved accuracy, less complex programming, and a lower cost of ownership (COO). Their tight integration lets them protect the device under test (DUT) from damage due to accidental overloads, thermal runaway, and other dangers. It also makes SMU instruments ideal for characterizing and testing semiconductors and other non-linear devices and materials.

SMU vs. Power Supply
Given that an SMU instrument integrates the functions of a power supply with a digital multimeter, how exactly
does the performance of an SMU’s source differ from that of a typical...

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