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Chapter 7
Counters
X Series User Manual
7-18
ni.com
Hardware-Timed Single Point Frequency
Measurement
hardware-timed single point (HWTSP) freq
u
ency meas
u
rements can either
be a single freq
u
ency meas
u
rement or an average between sample clocks.
Use CI.Freq.EnableAveraging to set the behavior. For hardware-timed
single point, the defa
u
lt is False. Refer to the
Sample Clocked Buffered
Frequency Measurement
section for more information.
Figure 7-17.
Hardware-Timed Single Point Frequency Measurement
Note
(NI USB-634
x
/635
x
/636
x
Devices)
X Series USB devices do not s
u
pport
hardware-timed single point (HWTSP) operations.
Choosing a Method for Measuring Frequency
The best method to meas
u
re freq
u
ency depends on several factors
incl
u
ding the expected freq
u
ency of the signal to meas
u
re, the desired
acc
u
racy, how many co
u
nters are available, and how long the meas
u
rement
can take. For all freq
u
ency meas
u
rement methods, ass
u
me the following:
fx
is the freq
u
ency to be meas
u
red if no error
fk
is the known so
u
rce or gate freq
u
ency
measurement time
(
T
)
is the time it takes to meas
u
re a single sample
Divide down (
N
)
is the integer to divide down meas
u
red freq
u
ency,
only
u
sed in large range two co
u
nters
fs
is the sample clock rate, only
u
sed in sample
clocked freq
u
ency meas
u
rements
G
a
te
S
o
u
rce
Sa
mple
Clock
Co
u
nter Armed
6
4
6
L
a
tched
V
a
l
u
e
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