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Number 810 Application Note Optimizing Switch/Read Rates with Series Keithley Series 2000 DMMs and 7001/7002 Switch Systems Introduction DUT The period of time an instrument requires to perform a specific measurement is only one factor in the overall equation of test system timing. Typical testing applications often require measuring several points of the DUT with the same instrument, DMM Switch DUT such as a multimeter. A multiplexer is typically used to switch the test signals automatically from point to point. Multiplexing can be done with relays or solid-state switching devices. The switching devices are normally housed in a mainframe that pro- DUT vides the card cage facility, drive lines and test instruction para- Figure 1. DMM/Switch Configuration meters. Keithley offers a variety of flexible measurement and switching solutions for these multipoint testing applications, including the Series 2000 line of digital multimeters and Model Integration rate--The integration rate is the time it takes the 7001 and 7002 switch mainframes. A/D converter to "look" at the input signal. The integration time affects the usable resolution, the amount of reading noise, and The rate at which a test is performed is crucial to test the ultimate reading rate of the measurement. The optimum inte- engineers because the faster the test is completed with reliable gration time setting for a given application depends on the mea- results, the more devices that can be tested in same period of surement requirements. If speed is the most important considera- time. Manufacturing/production facilities are always seeking opti- tion, then the smallest integration rate would be used (0.01 mum speed in their test systems. This application note addresses power line cycles or PLCs) at the expense of additional reading the factors that affect test system speed. These factors are noise and less usable resolution. For maximum common mode generally additive, but their effect on total system speed varies. and normal mode rejection, the larger integration rate would be Test engineers use the word "throughput" to define overall used (up to 50 PLCs). This would produce the most stable, accu- system speed. Throughput encompasses a variety of factors, rate and highest resolution readings. See Tables 1 and 2 for inte- including measurement source