User's Manual

NI cDAQ-9172 User Guide and Specifications 42 ni.com
Counter Input Applications
Counting Edges
In edge counting applications, the counter counts edges on its Source after
the counter is armed. You can configure the counter to count rising or
falling edges on its Source input. You also can control the direction of
counting (up or down).
The counter values can be read on demand or with a sample clock.
Single-Point (On-Demand) Edge Counting
With single-point (on-demand) edge counting, the counter counts the
number of edges on the Source input after the counter is armed. On-demand
refers to the fact that software can read the counter contents at any time
without disturbing the counting process. Figure 16 shows an example of
single-point edge counting.
Figure 16. Single-Point (On-Demand) Edge Counting
You also can use a pause trigger to pause (or gate) the counter. When the
pause trigger is active, the counter ignores edges on its Source input. When
the pause trigger is inactive, the counter counts edges normally.
Counter Armed
SOURCE
Counter Value 1 0 5 4 3 2