Log In   |  Register Free Newsletter Subscription
Global TMW:
Skip navigation
Zibb
Subscribe to Test & Measurement World
RSS
Reprints/License
Print
Email
Average Rating:
  • (0)
    Rate this:
  • How to measure display jitter

    Martin Rowe, Senior Technical Editor -- Test & Measurement World, 8/1/2009 2:00:00 AM

    All serial data streams and clocks have jitter (the difference between the arrival of an edge and the expected time of arrival). The jitter you see on an oscilloscope is a function of the signal's timing jitter and amplitude noise, plus the jitter and noise that the oscilloscope adds to the signal.



    A histogram shows the distribution of jitter in a rising edge. Courtesy of Agilent Technologies. 

    Download the paper “The evolution of trigger jitter” by Steve Draving, hardware engineer at Agilent Technologies.

    The jitter that an oscilloscope adds to the signal you see (call it display jitter) is a combination of the instrument's trigger noise and trigger jitter. Noise on an input signal produces a timing error in the displayed signal. If, at the start of a rising edge, noise has pulled a signal's amplitude low, the rising signal will cross a threshold point later than it would in a noise-free signal.

    Trigger noise will also add jitter because it affects the point where an edge crosses the trigger level. The amount that trigger noise contributes to display jitter depends on the input signal's slew rate. The greater the slew rate (faster rise or fall time), the less display jitter you will see.

    Oscilloscopes have traditionally measured display jitter (but called it trigger jitter) using a histogram (figure). But in some oscilloscopes, hardware has improved to where trigger noise dominates display jitter, making the trigger jitter component negligible. In addition, some oscilloscopes can mathematically remove most of the instrument's display jitter, producing a waveform that appears to have no noise or jitter at the trigger point.

    Because of those factors, the traditional measurement won't work. You can, though, use a different technique to measure an oscilloscope's display jitter. It involves using a sine wave and employing frequency-domain techniques. To learn how the technique works and how to apply it, download the paper “The evolution of trigger jitter” by Steve Draving, hardware engineer at Agilent Technologies.

    Average Rating:
  • (0)
    Rate this:
  • RSS
    Reprints/License
    Print
    Email
    Reed Business Information Resource Center

    Featured Company


    Related Resources

    Advertisement

    Related Microsite Content

    Related Links

    • No Related Content Available

    More Content
    • Blogs
    • Webcasts

    Sorry, no blogs are active for this topic.

    » VIEW ALL BLOGS RSS

    EDN's Designing with LEDs
    Advertisement
    TMW Video - www.tmworld.com/video/
    NEWSLETTERS
    Test Industry News
    Automotive, Aerospace & Defense
    Communications Test
    Design, Test & Yield
    Machine-Vision & Inspection
    Instrumentation



    Please read our Privacy Policy

    About Us   |   Advertising Info   |   Site Map   |   Contact Us   |   FREE Subscription   |   Editorial Calendar
    © 2010 Reed Business Information, a division of Reed Elsevier Inc. All rights reserved.
    Use of this Web site is subject to its Terms of Use | Privacy Policy
    Please visit these other Reed Business sites