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Chapter 2 Function Reference — GPCTR_Set_Application
©
National Instruments Corporation 2-239 NI-DAQ FRM for PC Compatibles
Figure 2-26.
Buffered Period Measurement when No Source Edges Are Present between Gate Edges
application = ND_BUFFERED_SEMI_PERIOD_MSR
In this application, the counter is used for the continuous measurement of the time interval
between successive transitions of the gate signal. By default, those are all transitions of the
signal on the line given in Table 2-25. The counter counts the 20 MHz internal timebase
(
ND_INTERNAL_20_MHZ), so the resolution of measurement is 50 ns. The counter counts up
starting from 0; its contents are placed in the buffer after an edge is detected on the gate; the
counter then starts counting up from 0 again. NI-DAQ transfers data from the counter into the
buffer until the buffer is filled; the counter is disarmed at that time.
Note The counter will start counting as soon as you arm it. Be aware of this when you
interpret the first count in your buffer.
Figure 2-27.
Buffered Semi-Period Measurement when No Source Edges Are Present between Gate Edges
Source
Gate
Buffer
2143651789 325416324
Measured
Period
Measured
Period
Measured
Period
Measured
Period
9 9
9
9
9
9
9
9
9
4
The instant
you arm
the counter
Warning
Source
Buffer
3
Gate
1
312
45
2
4
12
12
3
12
1
2
Measured
Semi-Period
3
Measured
Semi-Period
Measured
Semi-Period
Measured
Semi-Period
3
3
5
3
2
4
3
2
2
4
3
2
2
5
4
3
2
2
2
5
4
3
2