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Normal: In this acquisition mode, the oscilloscope samples the signal in evenly spaced intervals to establish the
waveform. This mode accurately represents signals in most time. However, it does not acquire rapid variations
in the analog signal that may occur between two samples, which can result in aliasing and may cause narrow
pulses to be missed. In such cases, you should use the Peak Detect mode to acquire data.
Peak Detect: In this acquisition mode, the oscilloscope gets the maximum and minimum values of the input
signal over each sample interval and uses these values to display the waveform. In this way, the oscilloscope
can acquire and display those narrow pulses that may have otherwise been missed in Normal mode. However,
noise will appear to be higher in this mode.
Average: In this acquisition mode, the oscilloscope acquires several waveforms, averages them, and displays
the resulting waveform. You can use this mode to reduce random noise.
Equivalent Acquisition: This kind of acquisition can be utilized for periodic signals. In case the acquisition rate
is too low when using the real-time acquisition, the oscilloscope will use a fixed rate to acquire data with a
stationary tiny delay after each acquisition of a frame of data. After repeating this acquisition for N times, the
oscilloscope will arrange the acquired N frames of data by time to make up a new frame of data. Then the
waveform can be recovered. The number of times N is related to the equivalent acquisition rate.
Time Base: The oscilloscope digitizes waveforms by acquiring the value of an input signal at discrete points.
The time base helps to control how often the values are digitized. Use the SEC/DIV knob to adjust the time base
to a horizontal scale that suits your purpose.
4.4
Waveform Scaling and Positioning
The display of waveforms on the screen can be changed by adjusting their scale and position. Once the scale
changes, the waveform display will increase or decrease in size. Once the position changes, the waveform will move
up, down, right, or left.
The channel reference indicator (located on the left of the graticule) identifies each waveform on the screen. It points
to the ground level of the waveform record.
Vertical Scale and Position:
The vertical position of a waveform can be changed by moving it up and down on the screen. To compare data, you
may align a waveform over another. When you push the VOLTS/DIV button to change the vertical scale of a
waveform, the waveform display will contract or expand vertically to the ground level.
Horizontal Scale and Position:
You can adjust the HORIZONTAL POSITION control to view waveform data before the trigger, after the trigger, or
some of each. When you change the horizontal position of a waveform, you are actually changing the time between
the trigger position and the screen center.
For example, if you want to find out the cause of a glitch in your test circuit, you should trigger on the glitch and make
the pretrigger period long enough to capture data before the glitch. Then you can analyze the pretrigger data and
perhaps find the cause. You are allowed to change the horizontal scale of all the waveforms by turning the SEC/DIV
knob. For example, you may want to see just one cycle of a waveform to measure the overshoot on its rising edge.
