High Frequency With Two Counters - National Instruments DAQ X Series User Manual

Chapter 7 Counters
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.

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.
Counter 0 is always paired with Counter 1. Counter 2 is always paired with
Note
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.
X Series User Manual
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fx
fx
Gate
1
fk
Source
fk
Single Period
Measurement
Figure 7-12. Low Frequency with One Counter
7-14
Interval Measured
2 3 ... ... N
N
Period of fx =
fk
fk
Frequency of fx =
N
ni.com