Figure 71. Buffered Position Measurement
1
3
1
Ch A
Ch B
3
1
0
2
4
Count
Buffer
Sample Clock
(Sample on Rising Edge)
Counter
Armed
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.
After the counter has been armed and an active edge occurs on the Aux input, the counter
counts the number of rising (or falling) edges on the Source. The counter ignores additional
edges on the Aux input.
The counter stops counting upon receiving an active edge on the Gate input. The counter
stores the count in the FIFO.
You can configure the rising or falling edge of the Aux input to be the active edge. You can
configure the rising or falling edge of the Gate input to be the active edge.
Use this type of measurement to count events or measure the time that occurs between edges
on two signals. This type of measurement is sometimes referred to as start/stop trigger
measurement, second gate measurement, or A-to-B measurement.
Refer to the following sections for more information about the cRIO controller edge-
separation measurement options:
•
Single Two-Signal Edge-Separation Measurement
•
Implicit Buffered Two-Signal Edge-Separation Measurement
•
Sample Clocked Buffered Two-Signal Separation Measurement
Single Two-Signal Edge-Separation Measurement
With single two-signal edge-separation measurement, the counter counts the number of rising
(or falling) edges on the Source input occurring between an active edge of the Gate signal and
an active edge of the Aux signal. The counter then stores the count in the FIFO and ignores
other edges on its inputs. Software then reads the stored count.
The following figure shows an example of a single two-signal edge-separation measurement.
NI cRIO-905x User Manual
|
© National Instruments
|
85
