Hardware-Timed Single Point Frequency Measurement; Choosing A Method For Measuring Frequency - National Instruments DAQ X Series 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
Frequency Measurement
Counter Armed
Gate
Source
Sample
Clock
Latched
Value
Note (NI USB-634x/635x/636x Devices)
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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Figure 7-17. Hardware-Timed Single Point Frequency Measurement
X Series USB devices do not support
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
7-18
Sample Clocked Buffered
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