© National Instruments | 5-9
NI cDAQ-9181/9184/9188/9191 User Manual
Figure 5-10 shows an example of a sample clocked buffered pulse measurement.
Figure 5-10. Sample Clocked Buffered Pulse Measurement
Note If a pulse does not occur between sample clocks, an overrun error occurs.
For information about connecting counter signals, refer to the Default Counter/Timer Routing
section.
Semi-Period Measurement
In semi-period measurements, the counter measures a semi-period on its Gate input signal after
the counter is armed. A semi-period is the time between any two consecutive edges on the Gate
input.
You can route an internal or external periodic clock signal (with a known period) to the Source
input of the counter. The counter counts the number of rising (or falling) edges occurring on the
Source input between two edges of the Gate signal.
You can calculate the semi-period of the Gate input by multiplying the period of the Source
signal by the number of edges returned by the counter.
Refer to the following sections for more information about semi-period measurement options:
• Single Semi-Period Measurement
• Implicit Buffered Semi-Period Measurement
Refer to the Pulse versus Semi-Period Measurements section for information about the
differences between semi-period measurement and pulse measurement.
Single Semi-Period Measurement
Single semi-period measurement is equivalent to single pulse-width measurement.
Counter
Armed
Gate
Source
HL
2
2
HL
22
3
3
Sample
Clock
S1
S2
Buffer
2
2
3
3
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