National Instruments NI USB-621x - Manual (Page 112)

Chapter 9 Counters
NI USB-621x User Manual 9-32 ni.com
the signal goes high or vice versa. For continuous pulse generations, the
counter stops generating pulses while the external trigger signal is low and
resumes when the signal goes high or vice versa.
When using a pause trigger, the pause trigger source is routed to the
Counter n Gate signal input of the counter.
Other Counter Features
Sample Clock
When taking counter measurements, you can enable a sample clock. When
you use a sample clock, measurements are saved after an active edge of the
sample clock. Figure 9-29 shows an example of using a sample clock with
a buffered period measurement. In this example, a period is defined by two
consecutive rising edges of the Gate.
Figure 9-29. Sample Clock Example
SOURCE
GATE
BUFFER
4
Counter Armed
SAMPLE CLOCK
4 4
3
TIME N
COUNTER VALUE
t
0
t
1
t
2
t
3
t
4
t
5
1 2 3 4 1 2 1 2 3 1