Chapter 7
Counters
©
National Instruments
7-9
X Series User Manual
Pulse Measurement
In p
u
lse meas
u
rements, the co
u
nter meas
u
res the high and low time of a
p
u
lse on its Gate inp
u
t signal after the co
u
nter is armed. A p
u
lse is defined
in terms of its high and low time, high and low ticks or freq
u
ency and d
u
ty
cycle. This is similar to the p
u
lse-width meas
u
rement, except that the
inactive p
u
lse is meas
u
red as well.
Yo
u
can ro
u
te an internal or external periodic clock signal (with a known
period) to the So
u
rce inp
u
t of the co
u
nter. The co
u
nter co
u
nts the
n
u
mber of rising (or falling) edges occ
u
rring on the So
u
rce inp
u
t
between two edges of the Gate signal.
Yo
u
can calc
u
late the high and low time of the Gate inp
u
t by m
u
ltiplying
the period of the So
u
rce signal by the n
u
mber of edges ret
u
rned by the
co
u
nter.
Refer to the following sections for more information abo
u
t X Series p
u
lse
meas
u
rement options:
•
Single Pulse Measurement
•
Implicit Buffered Pulse Measurement
•
Sample Clocked Buffered Pulse Measurement
•
Hardware-Timed Single Point Pulse Measurement
Single Pulse Measurement
Single (on-demand) p
u
lse meas
u
rement is eq
u
ivalent to two single
p
u
lse-width meas
u
rements on the high (H) and low (L) ticks of a p
u
lse, as
shown in Fig
u
re 7-8.
Figure 7-8.
Single (On-Demand) Pulse Measurement
Co
u
nter
Armed
G
a
te
S
o
u
rce
H L
7 10
7
10
L
a
tched
V
a
l
u
e
9
8
7
6
5
4
3
2
1
5
6
4
3
2
1
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