Programming instructions

Chapter 25 Measuring Pulse Width
© National Instruments Corporation 25-5 LabVIEW Data Acquisition Basics Manual
The
valid?
output of the example VI indicates whether the counter
measured the pulse without overflowing (reaching TC). However,
valid?
does not tell you whether a whole pulse was measured when measuring a
pulse within a pulse train. For a complete description of this example, refer
to the information found in
Windows»Show VI Info…
.
8253/54
Figure 25-7 shows the diagram of the Measure Short Pulse Width
(8253) VI located in
labview\examples\daq\counter\8253.llb
.
Figure 25-7.
Diagram of Measure Short Pulse Width (8253) VI
This VI counts the number of cycles of the internal timebase of
Counter 0
to measure a high pulse width. You can measure a single pulse or a pulse
within a train of multiple pulses. However, the pulse must occur after the
counter starts. This means it may be difficult to measure a pulse within a
fast pulse train because the counter uses high level gating. If you want to
measure a low pulse width, you need to insert a 7404 inverter chip between
your pulse source and the GATE input of counter 0.