Programming instructions

Chapter 26 Measuring Frequency and Period
© National Instruments Corporation 26-3 LabVIEW Data Acquisition Basics Manual
Connecting Counters to Measure Frequency and Period
Figure 26-3 shows typical external connections for measuring frequency.
In the figure, your device provides the signal with the frequency to be
measured to the SOURCE (CLK) of
counter
. It can optionally control the
GATE of
counter-1
. The OUT of
counter-1
supplies a known pulse to the
GATE of
counter
. Finally,
counter
counts the number of cycles of the
unknown pulse during the known GATE pulse.
Figure 26-3.
External Connections for Frequency Measurement
DAQ-STC, Am9513
Figure 26-4 shows typical external connections for measuring period.
In the figure, your device provides the signal with the period to be
measured to the GATE of
counter
. A timebase of known frequency is
supplied to the SOURCE. This is usually an internal timebase, but it could
be externally supplied. It is important that the counting range of your
counter is not exceeded during the period measurement. The range of the
Am9513 is 65,335, and the range of the DAQ-STC is 16,777,216. If the
counting range is exceeded, you can pick a slower internal timebase.
Figure 26-4.
External Connections for Period Measurement