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Block Diagram Descriptions
Theory of Operation
3Ć10
If auto trigger mode is selected, the timebase will generate its own trigger
signal after 20 ms. If normal trigger mode is selected, the CSA 803A will wait
for trigger signals.
The High Frequency On/Off Control selects the state of the trigger hysteresis
in the direct trigger path.
High Frequency On removes trigger hysteresis and improves sensitivity
when the trigger signal edge slew rate is 1 V/ns or greater, typically a
320 mV
pĆp
, 1 GHz sine wave. See Figure 3Ć1.
High Frequency Off retains trigger hysteresis while improving noise rejection
at low frequencies, when the trigger edge slew rate is less than 1 V/ns. It
can be used at any frequency if the trigger signal amplitude reliably triggers
the CSA 803A. See Figure 3Ć1. This is the default setting after initialization.
<1 V/ns
HF Off
960 mV
1 GHz
>1 V/ns
HF On
640 mV
320 mV
2 GHz 3 GHz 4 GHz
Frequency
V
in pĆp
Figure 3Ć1:ăTrigger Edge Slew Rate for High Frequency Selection
The Enhanced Triggering ON/Off Control selects the state of the metastable
trigger rejection feature in the direct trigger path.
Enhanced Triggering On directs the timebase to detect metastable trigger
events and reject the acquired data. The data is reacquired at the next
trigger event.
Enhanced Triggering Off allows the timebase to acquire and display metastĆ
able trigger events.
The Trigger Holdoff Control in the trigger menu programs the trigger holdoff
value.
Auto Holdoff is the default mode. This mode automatically programs Actual
Holdoff to the minimum possible value. It depends only on the time base
settings and is updated when the Main Size and Main Position values