User`s manual

46 Operation Theory
Figure 4-25: Analog trigger block diagram
The trigger signal asserts when an analog trigger condition is
meet. There are five analog trigger conditions in DAQ/PXI-2500
SERIES. DAQ/PXI-2500 SERIES uses 2 threshold voltages:
Low_Threshold and High_Threshold to compose 5 different trigger
conditions. Users can con-figure the trigger conditions easily via
software.
Below-Low analog trigger condition
Figure 4-26 shows the below-low analog trigger condition, the
trigger signal asserts when the input analog signal is lower than
the Low_Threshold voltage. High_Threshold setting is not used
in this trigger condition.
Trigger Level digital setting Trigger voltage
0xFF 9.92V
0xFE 9.84V
--- ---
0x81 0.08V
0x80 0
0x7F -0.08V
--- ---
0x01 -9.92V
0x00 -10V
Table 4-8: Analog trigger SRC1(EXTATRIG) ideal transfer characteristic