Tektronix TDS1000B Series Operator's Manual page 216

5
Using TRIGGER Controls
This eye diagram display shows that the positive and
negative transition edges of the signal are all synchronized
with the clock, as is expected. When the edges are not
stable relative to the clock, then jitter is occurring. This is a
very important issue for communications signals.
This procedure is useful in scenarios where you need to use
an external trigger source to observe the timing
relationships on the signals connected to the other available
channels. In a complex microprocessor circuit, you may
need to simultaneously observe the timing on all waveform
channels, while using the external trigger input as another
source for triggering.
The EXT TRIG input has a 10X probe connected to it. As a
result, the trigger level is actually 10 times more than that
shown on the display. You can further extend the external
trigger level range by selecting the EXT/5 trigger source.
The EXT/5 option further divides the signal from the external
source by five to increase the trigger level range.
5-16 TDS1000B and TDS2000B Series Oscilloscopes – Operator Training Kit