3-6
Triggering the Oscilloscope
To select trigger Coupling
To select trigger Coupling
1Press the Mode/Coupling key.
2Press the
Coupling softkey, then select DC, AC, or LF Reject coupling.
DC coupling allows dc and ac signals into the t rigger path.
AC coupling places a high-pass filter (3.5 Hz for 54620-series analog channels,
10 Hz for 54640-series analog channels, and 3.5 Hz for all External trigger
inputs) in the trigger path removing any DC offset voltage from the trigger
waveform. Use AC coupling to get a stable edge trigger when your waveform
has a large DC offset.
LF (low frequency) Reject coupling places a 50-kHz high-pass filter in series
with the trigger waveform. Low frequency reject removes any unwanted low
frequency components from a trigger waveform, such as power line
frequencies, that can interfere with proper triggering. Use this coupling to
get a stable edge trigger when your waveform has low frequency noise.
TV coupling is normally grayed-out, but is automatically selected when TV
trigger is enabled in the Trigger More menu.
To select Noise Reject and HF Reject
1Press the Mode/Coupling key.
2Press the
Noise Rej softkey to select noise reject or press the HF Reject
softkey to select high frequency reject.
Noise Rej adds additional hysteresis to the trigger circuitry. When noise reject
is on, the trigger circuitry is less sensitive to noise but may require a greater
amplitude waveform to trigger the oscillosco pe.
HF Reject adds a 50 kHz low-pass filter in the trigger path to remove high
frequency components from the trigger waveform. You can use HF Reject to
remove high-frequency noise, such as AM or FM broadcast stations or from
fast system clocks, from the trigger path.