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Edge Triggering
TDS 620A, 640A, & 644A User Manual
Figure 3-19: Main Trigger Menu — Edge Type
Coupling
To select the coupling you want:
Press TRIGGER MENU ➞ Type (main) ➞ Edge (pop-up) ➞ Cou-
pling (main) ➞ DC, AC, HF Rej, LF Rej, or Noise Rej (side).
DC
passes all of the input signal. In other words, it passes both AC and
DC components to the trigger circuit.
AC
passes only the alternating components of an input signal (above
30 Hz). It removes the DC component from the trigger signal.
HF Rej removes the high frequency portion of the triggering signal. That
allows only the low frequency components to pass on to the triggering
system to start an acquisition. High frequency rejection attenuates signals
above 30 kHz.
LF Rej does the opposite of high frequency rejection. Low frequency
rejection attenuates signals below 80 kHz.
Noise Rej provides lower sensitivity. Noise Rej requires additional signal
amplitude for stable triggering, reducing the chance of falsely triggering
on noise.