CEM DT-9989, Руководство пользователя, Страница: 45 / 68

2-8 1 Trigger Mode
2 9 Channel
2-10 FFT frequency spectrum analysis
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2 kinds of trigger mode for the oscilloscope: raising edge and falling edge. When signal
voltage across trigger electrical level, raising and falling edge of input signal is adopted for
triggering.
Raising edge setup: press “setup” “trigger” “raising edge” “save and quit”.
Falling edge setup: press “setup” “trigger” “falling edge” “save and quit”.
•If select “setup” “trigger” “no trigger” “save and quit”, the oscilloscope may lose
synchronizing signal and any signal measured by fast display.
•Oscilloscope vertical response should be slightly greater than its bandwidth, so that FFT
frequency spectrum can be higher than effective frequency of oscilloscope bandwidth.
However, amplitude close to or higher than the bandwidth will not be accurate.
•If channel coupling mode is DC, user can measure DC component of signal by observing
the difference between waveform and signal ground.
•If coupling mode is AC, DC component is filtered in the signal. This mode makes user
easily display the AC component of signal with higher sensitivity.
Channel Settings
•Channel coupling settings
Measured signal is sinusoidal signal containing DC bias:
•Press “setup”
“coupling” ”AC”, select AC coupling mode. DC component in measured
signal is separated.
•Press “setup” “coupling” “DC”, select DC coupling mode. DC and AC component in
measured signal can all pass.
Time signal can be converted into frequency component (frequency spectrum) by using FFT
mathematical operation (Fast Fourier Transform). Observe following signals by FFT mathematical
mode:
•Analyze harmonic wave in power line
•Measure harmonic wave content and distortion in system
•Measure impulse response of filter and system
•Analyze oscillation
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Oscilloscope Section