Programming instructions

Chapter 26 Measuring Frequency and Period
© National Instruments Corporation 26-5 LabVIEW Data Acquisition Basics Manual
Am9513
Figure 26-6 shows the Measure Frequency-Easy (9513) VI located in
labview\examples\daq\Am9513.llb
. This example uses the
Easy VI, Measure Frequency which can be found in
Functions»
Data Acquisition»Counter
.
Figure 26-6.
Diagram of Measure Frequency-Easy (9513) VI
This VI initiates the counter to count the number of rising edges of a
TTL signal at the SOURCE of counter during a known pulse at the GATE
of counter. The width of that known pulse is determined by gate width.
Frequency is the output for this example, and period is calculated by
taking the inverse of the frequency. The
valid?
output lets you know if
the measurement completed without an overflow. The number of counters
to use input lets you choose one counter for 16-bit measurement or two
counters for 32-bit measurement. Remember that you must externally
wire your signal to be measured to the SOURCE of counter, and the OUT
of
counter-1
must be wired to the GATE of counter. For a complete
description of this example, refer to the information found in
Windows»Show VI Info…
.