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Chapter 7
Counters
Hardware-Timed Single Point Frequency Measurement
Hardware-timed single point (HWTSP) frequency measurements can either be a single
frequency measurement or an average between sample clocks. Use CI.Freq.EnableAveraging to
set the behavior. For hardware-timed single point, the default is False. Refer to the
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)
USB X Series devices do not support
hardware-timed single point (HWTSP) operations.
Choosing a Method for Measuring Frequency
The best method to measure frequency depends on several factors including the expected
frequency of the signal to measure, the desired accuracy, how many counters are available, and
how long the measurement can take. For all frequency measurement methods, assume the
following:
fx
is the frequency to be measured if no error
fk
is the known source or gate frequency
measurement time
(
T
)
is the time it takes to measure a single sample
Divide down (
N
)
is the integer to divide down measured frequency, only used in
large range two counters
fs
is the sample clock rate, only used in sample clocked frequency
measurements
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
Summary of Contents for DAQ X NI 634 Series
Page 1: ...PXIe 6349...
