Measurements and Math Functions 5
InfiniiVision 7000B Series Oscilloscopes User’s Guide 201
3 To make cursors measurements, press the [Cursors] key and set the
Source softkey to Math: f(t).
Use the X1 and X2 cursors to measure frequency values and difference
between two frequency values (X). Use the Y1 and Y2 cursors to
measure amplitude in dB and difference in amplitude (Y).
4 To make other measurements, press the [Meas] key and set the Source
softkey to Math: f(t).
You can make peak-to- peak, maximum, minimum, and average dB
measurements on the FFT waveform. You can also find the frequency
value at the first occurrence of the waveform maximum by using the X
at Max Y measurement.
The following FFT spectrum was obtained by connecting the front panel
Probe Comp signal (approximately 1.2 kHz square wave) to channel 1. Set
sweep speed to 5 ms/div, vertical sensitivity to 500 mV/div, Units/div to
10 dBV, Offset to - 34.0 dBV, Center frequency to 5.00 kHz, frequency Span
to 10.0 kHz, and window to Hanning.
Scale and offset considerations
If you do not manually change the FFT scale or offset settings, when you turn the horizontal
sweep speed knob, the span and center frequency settings will automatically change to
allow optimum viewing of the full spectrum. If you do manually set scale or offset, turning
the sweep speed knob will not change the span or center frequency settings, allowing you
see better detail around a specific frequency. Pressing the FFT Preset softkey will
automatically rescale the waveform and span and center will again automatically track the
horizontal sweep speed setting.
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