Chapter 7 Counters
X Series User Manual 7-18 ni.com
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 Sample Clocked Buffered
Frequency Measurement section for more information.
Figure 7-17. Hardware-Timed Single Point Frequency Measurement
Note (NI USB-634x/635x/636x Devices)
X Series USB 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 u sed in sample
clocked frequency measurements
Gate
Source
Sample
Clock
Counter Armed
6
4
6
Latched
Value
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