3-18 | ni.com
Chapter 3 Counters
Figure 3-19. Frequency Measurement: High Frequency with Two Counters
With the known measurement time (T), which can be configured in CI.Freq.MeasTime, the
maximum error and maximum frequency error for this method are given by:
To use the High Frequency with 2 Counters method, configure the following:
• DAQmx Create channel (CI-Frequency)—Use this VI or function to create the channel.
• CI.Freq.MeasMeth—Set this property to High Frequency with 2 Counters
Note that this measurement method requires two counters:
• Counter 0 paired with Counter 1
• Counter 2 paired with Counter 3
• Counter 4 paired with Counter 5
• Counter 6 paired with Counter 7
Pulse
Pulse
12… P
T
Source Out
Counter M
Source
Gate
Counter N
Signal to
Measure
Signal to
Measure (f )
Counter
Timebase (f )
k
x
Maximum Error (%)
1
Tf
x
×
-------------= 100%×
Maximum Frequency Error (Hz)
1
T
---=
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