National Instruments Network Device DAQ S - Manual (Page 137)

Chapter 11 Triggering
© National Instruments Corporation 11-5 NI 6124/6154 User Manual
For the trigger to assert, the signal must first be below the low
threshold, then go above the high threshold. The trigger stays
asserted until the signal returns below the low threshold. The
output of the trigger detection circuitry is the internal Analog
Comparison Event signal, as shown in Figure 11-5.
Figure 11-5. Analog Edge Triggering with Hysteresis Rising Slope Example
– Analog Edge Trigger with Hysteresis (Falling Slope)—When
using hysteresis with a falling slope, you specify a trigger level
and amount of hysteresis. The low threshold is the trigger level;
the high threshold is the trigger level plus the hysteresis.
For the trigger to assert, the signal must first be above the high
threshold, then go below the low threshold. The trigger stays
asserted until the signal returns above the high threshold. The
output of the trigger detection circuitry is the internal Analog
Comparison Event signal, as shown in Figure 11-6.
Figure 11-6. Analog Edge Triggering with Hysteresis Falling Slope Example
Analog Comparison Event
Hysteresis
High threshold
(Level)
Low threshold
(Level – Hysteresis)
First signal must go
below low threshold
Then signal must
go above high threshold before
Analog Comparison Event asserts
Analog Comparison Event
Hysteresis
High threshold
(Level + Hysteresis)
Low threshold
(Level)
First signal must go
above high threshold
Then signal must go below low threshold
before Analog Comparison Event asserts