User`s guide

Making Measurements 4
5000 Series Oscilloscope User’s Guide 161
Differentiate
d/dt (differentiate) calculates the discrete time derivative of the
selected source. You can use differentiate to measure the
instantaneous slope of a waveform. For example, the slew rate
of an operational amplifier may be measured using the
differentiate function.
Because differentiation is very sensitive to noise, it is helpful to
set acquisition mode to Averaging in the Acquire menu.
d/dt plots the derivative of the selected source using the
“average slope estimate at 4 points” formula. The equation is:
Where
d = differential waveform
y = channel 1, 2, or function 1 + 2, 1 – 2, and 1 * 2 data points
i = data point index
∆t = point-to-point time difference
In Zoom mode, the d/dt function does not display in the zoomed
portion of the display.
1 Press the Math key, press the d/dt softkey, then press the
Settings softkey if you want to change the source, scaling, or
offset for the differentiate function.
• Source — selects the source for d/dt. The source can be any
oscilloscope channel, or math functions 1 + 2, 1 – 2, and
1*2.
• Scale — lets you set your own vertical scale factors for d/dt
expressed in units/second/division, where units can be V
(Volts), A (Amps), or W (Watts). Units are set in the
channel Probe menu. Press the Scale softkey, then turn the
Entry knob to rescale d/dt.
d
i
= y
i+4
+ 2y
i+2
– 2y
i-2
– y
i-4
8∆t