Pulse-Width Measurement; Single Pulse-Width Measurement; Implicit Buffered Pulse-Width Measurement - National Instruments NI cRIO-905x Series User Manual

Pulse-Width Measurement

In pulse-width measurements, the counter measures the width of a pulse on its Gate input
signal. You can configure the counter to measure the width of high pulses or low pulses on the
Gate signal.
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 on the Source
signal while the pulse on the Gate signal is active.
You can calculate the pulse width by multiplying the period of the Source signal by the
number of edges returned by the counter.
A pulse-width measurement will be accurate even if the counter is armed while a pulse train is
in progress. If a counter is armed while the pulse is in the active state, it will wait for the next
transition to the active state to begin the measurement.
Refer to the following sections for more information about cRIO controller pulse-width
measurement options:
•

Single Pulse-Width Measurement

•

Implicit Buffered Pulse-Width Measurement

• Sample Clocked Buffered Pulse-Width Measurement
Single Pulse-Width Measurement
With single pulse-width measurement, the counter counts the number of edges on the Source
input while the Gate input remains active. When the Gate input goes inactive, the counter
stores the count in the FIFO and ignores other edges on the Gate and Source inputs. Software
then reads the stored count.
The following figure shows an example of a single pulse-width measurement.
SOURCE
Counter Value
Latched Value
Implicit Buffered Pulse-Width Measurement
An implicit buffered pulse-width measurement is similar to single pulse-width measurement,
but buffered pulse-width measurement takes measurements over multiple pulses.
70 | ni.com | NI cRIO-905x User Manual
Figure 54. Single Pulse-Width Measurement
GATE
0 1 2
2