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Scaling and Positioning Waveforms
TDS 620A, 640A & 644A User Manual
2Ć23
You can adjust the vertical position of the selected waveform by moving it up
or down on the display. For example, when trying to compare multiple
waveforms, you can put one above another and compare them, or you can
overlay the two waveforms on top of each other. To move the selected
waveform turn the vertical POSITION knob.
You can also alter the vertical scale. The digitizing oscilloscope shows the
scale (in volts per division) for each active channel toward the bottom left of
the display. As you turn the vertical SCALE knob clockwise, the value deĆ
creases resulting in higher resolution because you see a smaller part of the
waveform. As you turn it counterĆclockwise the scale increases allowing you
to see more of the waveform but with lower resolution.
Besides using the position and scale knobs, you can set the vertical scale
and position with exact numbers. You do that with the Vertical menu Fine
Scale and Position selections and the general purpose knob and/or the
keypad.
Offset
Vertical offset changes where the channel reference indicator is shown with
respect to the graticule. Offset adds a voltage to the reference indicator
without changing the scale. That feature allows you to move the waveform
up and down over a large area without decreasing the resolution.
Offset is useful in cases where a waveform has a DC bias. One example is
looking at a small ripple on a power supply output. You may be trying to
look at a 100 mV ripple on top of a 15 V supply. The range available with
offset can prove valuable as you try to move and scale the ripple to meet
your needs.
Adjusting the horizontal position of waveforms moves them right or left on
the display. That is useful when the record length of the waveform is so large
(greater than 500 points) that the digitizing oscilloscope cannot display the
entire waveform record at one time. You can also adjust the scale of the
waveform. For example, you might want to see just one cycle of a waveform
to measure the overshoot on its rising edge.
You adjust the horizontal scale of the displayed waveform records using the
horizontal SCALE knob and the horizontal position using the horizontal
POSITION knob.
The digitizing oscilloscope shows the actual scale in the bottom right of the
display. The scale readout shows the time per division used. Since all live
waveforms use the same time base, the digitizing oscilloscope only displays
one value for all the active channels.
Vertical System
Horizontal System