Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity: How to Make the Most Accurate Digital Measurements
Digital storage oscilloscopes (DSO) are the primary tools used today by digital designers to perform signal integrity measurements such as setup/hold times, rise/fall times, and eye margin tests. High performance oscilloscopes are also widely used in university research labs to accurately characterize high-speed digital devices and systems, as well as to perform high energy physics experiments such as pulsed laser testing. In addition, general-purpose oscilloscopes are used extensively by Electrical Engineering students in their various EE analog and digital circuits lab courses.
The two key banner specifications than affect an oscilloscope's signal integrity measurement accuracy are bandwidth and sample rate. Most engineers and EE professors have a good idea of how much bandwidth they need for their digital measurements. However, there is often a lot confusion about required sample rate — and engineers often assume that scopes with the highest sample rate produce the most accurate digital measurements. But is this true?
When you select an oscilloscope for accurate, high-speed digital measurements, sampling fidelity can often be more important than maximum sample rate. Using side-by-side measurements on oscilloscopes with various bandwidths and sample rates, this presentation demonstrates a counterintuitive concept: scopes with higher sample rates can exhibit poorer signal fidelity because of poorly aligned interleaved analog-to-digital converters (ADCs). This presentation also will show how to easily characterize and compare scope ADC sampling fidelity using both time-domain and frequency-domain analysis techniques.
Who should view this webcast:
In the field of academics, this presentation can be first applied as a practical application and demonstration of theories presented in courses on digital signal processing. Secondly, when selecting high performance test equipment for electrical engineering and physics research labs, this presentation will provide tips on how to select and evaluate digital storage oscilloscopes for accurate reproduction of captured high-speed signals.
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Johnnie Hancock, Product Manager, Agilent Technologies Digital Test Division
Johnnie Hancock began his career with Hewlett-Packard in 1979 as an embedded hardware designer, and holds a patent for digital oscilloscope amplifier calibration. Johnnie is currently responsible for worldwide application support activities that promote Agilent’s digitizing oscilloscopes and he regularly speaks at technical conferences worldwide. Johnnie graduated from the University of South Florida with a degree in electrical engineering. In his spare time, he enjoys spending time with his four grandchildren and restoring his century-old Victorian home located in Colorado Springs.
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