Agilent Technologies ------------------------------------------------------------------------ Can I zoom in on a signal with my Infiniium scope for better jitter measurement resolution? - ------------------------------------------------------------------------ The faster a signal´s edges are, the less vertical noise will contribute to the jitter measurement. One way to make an edge appear faster on screen is to increase the vertical sensitivity, or decrease the volts per division. Some scope users will expand the signal far off of the screen to maximize the effect and to make the signal edge appear nearly vertical. This technique is acceptable within certain limits for sampling scope such as the Agilent 86100C. But it is not recommended for real-time scopes such as the Agilent 54800-series. Your scope should be scaled so that the signal occupies as much of the screen as possible without being clipped. If the signal is clipped off the screen, it will exceed the A/D converter´s range and possibly violate the scope´s dynamic range. This can do more harm to your measurement than good. If you are using a 54800-series Infiniium, a better approach is to use its Magnify function. This is a software expansion of the waveform that allows you to "zoom in" on a copy of the waveform, without overdriving the input amplifier or clipping the A/D converter. To use the Magnify function on Channel 1, follow these steps: 1. Click *Analyze | Math/FFT* 2. Under *Function 1*, check *Display On* 3. Under *Operator*, select *Magnify* 4. Under *Source 1*, select the channel that you wish to magnify 5. Under *Vertical*, select *Manual *and enter appropriate scaling factors 6. Click *Close * You can now measure peak-to-peak jitter with either a histogram or cursors. Note that there is a lower limit on the vertical scaling below which histogram data will not be gathered. ------------------------------------------------------------------------ © Agilent 2000-2004