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Digitizer/Oscilloscope Fundamentals

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Overview

This tutorial recommends tips and techniques for using National Instruments High-Speed Digitizers to build the most effective data sampling system possible. In this tutorial, you will learn fundamental information about the underlying theory of sampling with a high-speed digitizer and various methods to optimize the performance of your data sampling.

Table of Contents

  1. Digitizer Fundamentals
  2. User Applications Using Digitizers
  3. Example Programs
  4. Resources
  5. References

Digitizer Fundamentals

 

Bandwidth, Sample Rate and Nyquist Theorem
The two major components in a high-speed digitizer's analog front end are the analog input path and the analog-to-digital converter (ADC). The signals that you can capture with a digitizer are primarily determined by the bandwidth of the analog input path and the sample rate at which the ADC samples the conditioned (amplified, filtered, coupled, etc) waveform and converts the signal to digital values.

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Resolution
The resolution of a n-bit analog-to-digital Converter (ADC) is a function of how many parts the maximum votage signal can be divided into. A higher resolution digitizer allows you to capture smaller voltages. For example, with an 8-bit digitizer, you can capture differences of only 39 mV with a 10 V input range.  By contrast, a 14-bit digitizer can resolve voltage differences as small as 610 µV using the same input range.

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Record Length, Vertical Range and Offset, Input Coupling and Probing
This tutorial discusses how onboard memory, input range, signal coupling, and probing affect the measurements you take. 

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Frequency Domain Measurement Fundamentals
This tutorial discusses how characteristics of a digitizer including flatness, spurious free dynamic range (SFDR), signal-to-noise ratio (SNR), total harmonic distortion (THD), and SINAD will affect your measurements.

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FFT Analysis
Understand how a time-domain signal can be represented in the frequency domain, which can provide more information about a signal and make certain characteristics easier to visualize.  The Fourier transform converts a time domain representation of a signal into a frequency domain representation.

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Video Signal Measurement and Generation Fundamentals
This tutorial describes the basics of video signal measurement and generation by explaining the theory and giving practical examples. Topics discussed, include parts of the video signal, different video formats, color coding, and more.

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Triggering with Digitizers
A trigger is an external stimulus that initiates one or more instrument functions. Trigger stimuli include digital edges, software functions, and analog levels. This tutorial describes different trigger types that can be used with National Instruments digitizers.

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User Applications Using Digitizers

 

Microsoft Uses NI LabVIEW and PXI Modular Instruments to Develop Production Test System for Xbox 360 Controllers

 

 

 

 

Diagnostic Sonar Acquires and Processes Ultrasonic Phased Array Image Data with NI LabVIEW and PXI

 

 

 

 

Grass Valley Improves Test Time by 75 percent with Modular Instruments

 

 

 

Click here to view more customer applications using digitizers >>

Example Programs

 

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Resources

 

References

 

Downloads

pxitecharticle.pdf

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This tutorial (this "tutorial") was developed by National Instruments ("NI"). Although technical support of this tutorial may be made available by National Instruments, the content in this tutorial may not be completely tested and verified, and NI does not guarantee its quality in any way or that NI will continue to support this content with each new revision of related products and drivers. THIS TUTORIAL IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND AND SUBJECT TO CERTAIN RESTRICTIONS AS MORE SPECIFICALLY SET FORTH IN NI.COM'S TERMS OF USE (http://ni.com/legal/termsofuse/unitedstates/us/).