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TDS 620A, 640A & 644A User Manual
3Ć139
Waveform Differentiation
Advanced DSP Math (optional on TDS 620A & TDS 640A), provides waveĆ
form differentiation that allows you to display a derivative math waveform
that indicates the instantaneous rate of change of the waveform acquired.
Such waveforms are used in the measurement of slew rate of amplifiers and
in educational applications. You can store and display a derivative math
waveform in a reference memory, then use it as a source for another derivaĆ
tive waveform. The result is the second derivative of the waveform that was
first differentiated.
The math waveform, derived from the sampled waveform, is computed
based on the following equation:
Where: X is the source waveform
Y is the derivative math waveform
T is the time between samples
Y
n
+ (X
(n)1)
* X
n
)
1
T
Since the resultant math waveform is a derivative waveform, its vertical scale
is in volts/second (its horizontal scale is in seconds). The source signal is
differentiated over its entire record length; therefore, the math waveform
record length equals that of the source waveform.
To obtain a derivative math waveform:
1. Connect the waveform to the desired channel input and select that
channel.
2. Adjust the vertical and horizontal scales and trigger the display (or press
AUTOSET).
3. Press MORE ➞ Math1, Math2,orMath3 (main) ➞ Change Math
Definition (side) ➞ Single Wfm Math (main). See Figure 3Ć21.
4. Press Set Single Source to (side). Repeatedly press the same button
(or use the general purpose knob) until the channel source selected in
step 1 appears in the menu label.
Description
Operation