4-16
MegaZoom Concepts and Oscilloscope Operation
To setup the Horizontal time base
Roll mode
Roll mode causes the waveform to move slowly across the screen from right to
left. It only operates on time base settings of 500 ms/div and slower. If the
current time base setting is faster than the 500 ms/div limit, it will be set to
500 ms/div when Roll mode is entered.
In Normal horizontal mode, signal events occurring before the trigger are
plotted to the left of the trigger point (▼) and signal events after the trigger
plotted to the right of the trigger point.
In Roll mode there is no trig ger. The fixed re ference poi nt on the scre en is the
right edge of the screen and refers to the current moment in time. Events that
have occurred are scrolled to the left of the reference point. Since there is no
trigger, no pre-trigger information is availabl e.
If you would like to clear the display and restart an acquisition in Roll mode,
press the Single key.
Use Roll mode on low-frequency waveforms to yield a display much like a strip
chart recorder. It allows the waveform to roll across the display.
XY mode
XY mode changes the display from a volts-ver sus-time display to a
volts-versus-volts display. The time base is turned off, and Channel 1 amplitude
is plotted on the X-axis and Channel 2 amplitude is plotted on the Y-axis.
You can use XY mode to compare frequency and phase re lationships between
two si gnal s. XY mod e can als o be u sed w ith t rans duc ers t o dis pla y str ain v ers us
displacement, flow versus pressure, volts versus c urrent, or voltage versus
frequency.
Use the cursors to make measurements on XY mode waveforms.
For more information about using XY mode for measurements, refer to the
“Making Measurements” chapter.