Plateauing clock speeds impact test and measurement

November 23, 2015 // By Adam Foster and Shahram Mehraban
Adam Foster of National Instruments and Shahram Mehraban of Intel considers how plateauing clock speeds has an impact on test and measurement performance.

A large misconception is that test data is purely pass/fail, but this could not be further from the truth. Even though traditional, fixed-functionality instruments only send the results back to the host PC of a test system, they are hiding a lot of signal processing under their plastic shells. The processor inside your instrument determines the speed of your measurement. This is especially true for signal processing intensive measurements for applications such as RF, sound and vibration, and waveform-based oscilloscopes.

Figure 1. Signal processing dominates the total time for CPU-hungry measurements.

For example, even the fastest FFT-based spectrum analyzers on the market still spend only 20 percent of their measurement time actually acquiring the signal. The remaining 80+ percent is spent processing the signal for the given algorithm. If you apply this to an instrument released five years prior, the breakdown is even worse. The signal processing can end up dominating up to 95 percent of the measurement time. Because investing in a completely new portfolio of instrumentation each year is not an option, using antiquated test equipment to test modern, complex devices is a reality. Most test departments end up with a large performance gap between the processing power of their systems and their true processing needs.

Figure 2. Traditional box instruments with fixed CPUs exhibit a costly performance gap over their lifetimes.

Modular-based test systems feature three main and separate parts: the controller, the chassis, and the instrumentation. The controller works like an industrial PC and contains the CPU of a system. The main benefit of this approach is the ability to replace the CPU with the latest processing technology and keep the remaining components (chassis/backplane and instrumentation) as is in the test system. For most use cases, keeping the instrumentation and upgrading the processing extend the life of a modular test system well beyond that of a traditional instrument.

Figure 3. Modular test systems allow you to

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