Chapter 7
Counters
©
National Instruments Corporation
7-9
For information about connecting counter signals, refer to the
section.
Frequency Measurement
You can use the counters to measure frequency in several different ways.
You can choose one of the following methods depending on your
application:
•
Method 1: Measure Low Frequency with One Counter
—In this
method, you measure one period of your signal using a known
timebase. This method is good for low frequency signals.
You can route the signal to measure (F1) to the Gate of a counter. You
can route a known timebase (Ft) to the Source of the counter. The
known timebase can be 80MHzTimebase. For signals that might be
slower than 0.02 Hz, use a slower known timebase.
You can configure the counter to measure one period of the gate signal.
The frequency of F1 is the inverse of the period. Figure 7-10 illustrates
this method.
Figure 7-10.
Method 1
•
Method 1b: Measure Low Frequency with One Counter
(Averaged)
—In this method, you measure several periods of your
signal using a known timebase. This method is good for low to medium
frequency signals.
You can route the signal to measure (F1) to the Gate of a counter. You
can route a known timebase (Ft) to the Source of the counter. The
known timebase can be 80MHzTimebase. For signals that might be
slower than 0.02 Hz, use a slower known timebase.
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
