© National Instruments | 5-21
NI cDAQ-9181/9184/9188/9191 User Manual
Measurements Using Two Pulse Encoders
The counter supports two pulse encoders that have two channels—channels A and B.
The counter increments on each rising edge of channel A. The counter decrements on each rising
edge of channel B, as shown in Figure 5-21.
Figure 5-21. Measurements Using Two Pulse Encoders
For information about connecting counter signals, refer to the Default Counter/Timer Routing
section.
Buffered (Sample Clock) Position Measurement
With buffered position measurement (position measurement using a sample clock), the counter
increments based on the encoding used after the counter is armed. The value of the counter is
sampled on each active edge of a sample clock. The STC3 transfers the sampled values to host
memory using a high-speed data stream. The count values returned are the cumulative counts
since the counter armed event; that is, the sample clock does not reset the counter. You can route
the counter sample clock to the Gate input of the counter. You can configure the counter to
sample on the rising or falling edge of the sample clock.
Figure 5-22 shows an example of a buffered X1 position measurement.
Figure 5-22. Buffered Position Measurement
Two-Signal Edge-Separation Measurement
Two-signal edge-separation measurement is similar to pulse-width measurement, except that
there are two measurement signals—Aux and Gate. An active edge on the Aux input starts the
counting and an active edge on the Gate input stops the counting. You must arm a counter to
begin a two edge separation measurement.
Ch A
Ch B
Counter Value
2 3 54 344
1
3
1
Ch A
Ch B
3102 4
Count
Buffer
Sample Clock
(Sample on Rising Edge)
Counter
Armed
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