Hardware-Timed Single Point Frequency Measurement; Choosing A Method For Measuring Frequency - National Instruments PCIe-6323 User Manual

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
Figure 7-17. Hardware-Timed Single Point Frequency Measurement
Counter Armed
Gate
Source
Sample
Clock
Latched
Value
Note (NI USB-634
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
fk
measurement time (T)
Divide down (N)
fs
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section for more information.
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x x x
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is the frequency to be measured if no error
is the known source or gate frequency
is the time it takes to measure a single sample
is the integer to divide down measured frequency, only used in
large range two counters
is the sample clock rate, only used in sample clocked frequency
measurements
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USB X Series devices do not support
Sample
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