Chapter 7 Counters
X Series User Manual 7-14 ni.com
You can configure the counter to measure one period of the gate signal. The
frequency of fx is the inverse of the period. Figure 7-12 illustrates this
method.
Figure 7-12. Low Frequency with One Counter
High Frequency with Two Counters
For high frequency measurements with two counters, you measure one
pulse of a known width using your signal and derive the frequency of your
signal from the result.
Note Counter 0 is always paired with Counter 1. Counter 2 is always paired with
Counter 3.
In this method, you route a pulse of known duration (T) to the Gate of a
counter. You can generate the pulse using a second counter. You also can
generate the pulse externally and connect it to a PFI or RTSI terminal. You
only need to use one counter if you generate the pulse externally.
Route the signal to measure (fx) to the Source of the counter. Configure the
counter for a single pulse-width measurement. If you measure the width of
pulse T to be N periods of fx, the frequency of fx is N/T.
fx
fk
Gate
Source
123 … N
Single Period
Measurement
…
Period of fx =
N
Frequency of fx =
N
Interval Measured
fk
fk
fk
fx
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