National Instruments Network Device DAQ S - Manual (Page 138)

Chapter 11 Triggering
NI 6124/6154 User Manual 11-6 ni.com
• Analog Window Triggering—An analog window trigger occurs
when an analog signal either passes into (enters) or passes out of
(leaves) a window defined by two voltage levels. Specify the levels by
setting the window Top value and the window Bottom value.
Figure 11-7 demonstrates a trigger that asserts when the signal enters
the window.
Figure 11-7. Analog Window Triggering Mode (Entering Window)
Analog Trigger Accuracy
(NI 6124 Only) The analog trigger circuitry compares the voltage of the
trigger source to the output of programmable trigger DACs. When you
configure the level (or the high and low limits in window trigger mode), the
device adjusts the output of the trigger DACs. Refer to the specifications
document for your device to find the accuracy and resolution of the analog
trigger DACs.
To improve accuracy you can software-calibrate the analog trigger
circuitry. No hardware calibration is provided for the analog trigger
circuitry. In addition, the propagation delay from when a valid trigger
condition is met to when the analog trigger circuitry emits the Analog
Comparison Event may have an impact on your measurements if the trigger
signal has a high slew rate. If you find these conditions have a noticeable
impact on your measurements, you can perform software calibration on the
analog trigger circuitry by configuring your task as normal and applying a
known signal for your analog trigger. Comparing the observed results
against the expected results, you can calculate the necessary offsets to apply
in software to fine-tune the desired triggering behavior.
Top
Analog Comparison Event
Bottom