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Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity

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2011 ASEE Annual Conference & Exposition


Vancouver, BC

Publication Date

June 26, 2011

Start Date

June 26, 2011

End Date

June 29, 2011



Conference Session

ECE Division Poster Session

Tagged Division

Electrical and Computer

Page Count


Page Numbers

22.644.1 - 22.644.11



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Paper Authors


Johnnie Lynn Hancock Agilent Technologies

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Johnnie Hancock is a Product Manager at Agilent Technologies Digital Test Division. He 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.

Contact Information:

Johnnie Hancock,
Agilent Technologies,
1900 Garden of the Gods Rd.,
Colorado Springs, CO 80907,
+1 719-590-3183,

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Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity: How to Make the Most Accurate Digital MeasurementsIntroductionDigital storage oscilloscopes (DSO) are the primary tools used today by digital designers toperform signal integrity measurements such as setup/hold times, rise/fall times, and eye margintests. High performance oscilloscopes are also widely used in university research labs toaccurately characterize high-speed digital devices and systems, as well as to perform high energyphysics experiments such as pulsed laser testing. In addition, general-purpose oscilloscopes areused extensively by Electrical Engineering students in their various EE analog and digitalcircuits lab courses.The two key banner specifications than affect an oscilloscope’s signal integrity measurementaccuracy are bandwidth and sample rate. Most engineers and EE professors have a good idea ofhow much bandwidth they need for their digital measurements. However, there is often a lotconfusion about required sample rate — and engineers often assume that scopes with the highestsample rate produce the most accurate digital measurements. But is this true?When you select an oscilloscope for accurate, high-speed digital measurements, samplingfidelity can often be more important than maximum sample rate. Using side-by-sidemeasurements on oscilloscopes with various bandwidths and sample rates, this paperdemonstrates a counterintuitive concept: scopes with higher sample rates can exhibit poorersignal fidelity because of poorly aligned interleaved analog-to-digital converters (ADCs). Thispaper also will show how to easily characterize and compare scope ADC sampling fidelity usingboth time-domain and frequency-domain analysis techniques.In the field of academics, this paper can be first applied as a practical application anddemonstration of theories presented in courses on digital signal processing. Secondly, whenselecting high performance test equipment for electrical engineering and physics research labs,this paper will provide tips on how to select and evaluate digital storage oscilloscopes foraccurate reproduction of captured high-speed signals.

Hancock, J. L. (2011, June), Evaluating Oscilloscope Sample Rates vs. Sampling Fidelity Paper presented at 2011 ASEE Annual Conference & Exposition, Vancouver, BC. 10.18260/1-2--17925

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