Chapter 8
Counters
8-10
ni.com
Frequency Measurement
Yo
u
can
u
se the co
u
nters to meas
u
re freq
u
ency in several different ways.
Yo
u
can choose one of the following methods depending on yo
u
r
application:
•
Method 1: Measure Low Frequency with One Counter
—In this
method, yo
u
meas
u
re one period of yo
u
r signal
u
sing a known
timebase. This method is good for low freq
u
ency signals.
Yo
u
can ro
u
te the signal to meas
u
re (F1) to the Gate of a co
u
nter. Yo
u
can ro
u
te a known timebase (Ft) to the So
u
rce of the co
u
nter. The
known timebase can be 80MHzTimebase. For signals that might be
slower than 0.02 Hz,
u
se a slower known timebase.
Yo
u
can config
u
re the co
u
nter to meas
u
re one period of the gate signal.
The freq
u
ency of F1 is the inverse of the period. Fig
u
re 8-10 ill
u
strates
method 1.
Figure 8-10.
Method 1
F1
Ft
F1
Ft
G
a
te
S
o
u
rce
1 2
3
…
N
S
ingle Period
Me
asu
rement
…
Period of F1 =
N
Ft
Freq
u
ency of F1 =
N
Ft
Interv
a
l Me
asu
red
