Agilent Technologies 42A, 54621D To select trigger Coupling, To select Noise Reject and HF Reject

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 trigger 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 oscilloscope.

•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.

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