Roll Mode provides an instant display response when the oscilloscope is operating at very slow sweep speeds. Without it, the acquisition
must complete before the display will update.
Roll Mode is not available in the Acquisition Mode drop-down menu. It is automatically enabled at Horizontal Scale factors of 40 ms/div and
slower when running in Auto Trigger mode or in Single / Seq acquisition mode. The record length is limited to 1 M points when rolling.
Roll Mode is disabled when running in Normal Trigger mode. This can be selected with the front panel Trigger Mode button or the Trigger
Mode control on the MODE & HOLDOFF panel of the Trigger configuration menu.
Note: If Roll Mode is enabled, Average and Envelope will not be available in the Acquisition Mode drop-down list.
Coupling
Coupling determines whether an input signal is directly connected to the input channel (DC coupling) or connected through a DC blocking
capacitor (AC coupling).
All instruments and probes specify a maximum signal level. Do not exceed the limit, even momentarily, as the input channel or probe may
be damaged. Use external attenuators if necessary to prevent exceeding the limits.
The input resistance of each input channel can be 1 MΩ or 50 Ω. To properly terminate signals when using coaxial cables, or to support
active probes with different termination requirements, select the termination in the Channel menu Vertical Settings panel.
All probes expect a specific coupling and input termination. Both coupling and input termination are displayed on the screen. If the
instrument determines the coupling and termination required by the probe, either implicitly because of the TekProbe/TekVPI interface or
through performing a probe compensation, the instrument sets the required coupling and input termination.
Consider the following when you use 50 Ω termination with any channel:
• The instrument does not accurately display frequencies under 200 kHz if AC coupling is selected.
• The instrument reduces the maximum volts per division setting for the channel, since input amplitudes appropriate for the higher
settings would overload the 50 Ω input.
Scaling and positioning
Set vertical scaling, positioning, and DC offsets to display the features of interest on your waveform and to avoid clipping.
The display contains ten major divisions. This represents the maximum digitizing range of the instrument for any given vertical scale.
Vertical waveform data that is outside (above and/or below) the maximum range is clipped; that is, the data values exceed the digitizing
capability of the ADC at the current settings.
Set the horizontal scale, position, and resolution (record length) to include the acquired waveform record waveform attributes of interest
with good sampling density on the waveform. These settings define the horizontal acquisition window, described in .
Note: The terms vertical acquisition window and horizontal acquisition window refer to the vertical and horizontal range of the
segment of the input signal that the acquisition system acquires.
Vertical acquisition considerations
You can set the vertical scale, position, and offset of each channel independently of other channels.
The offset control subtracts a constant DC level from the input signal before the vertical scale factor is applied, and the vertical position
control adds a constant number of divisions of signal after the scale factor is applied to the resulting difference.
The vertical scale and position controls have the following effects on the waveform display and the displayed waveform:
The vertical volts per division you set determines the vertical size of the waveform display, allowing you to scale it to contain all of a
waveform amplitude or only part.
Waveform acquisition concepts
3 Series Mixed Domain Oscilloscope Printable Help
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