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By default, the counters measure the frequency on a default PFI terminal (refer to Chapter 5,
, for more information) and use an onboard 100 MHz clock as the
timebase. To change the signals used for this measurement, configure the following:
•
CI.Freq.Term—The signal-to-measure comes from an input terminal. To change the
signal-to-measure, set this property to a different terminal.
•
CI.CtrTimebase.Src—To change the signals used as the counter timebase, set this
property to a different terminal.
Period Measurement
Period measurements return the inverse result of Frequency measurements. Refer to the
section for more information.
The settings available for Period measurements are similar to Frequency measurements. For
example, use CI.Period.Term to change the signal-to-measure.
Pulse-Width Measurement
Note
This section describes Pulse-Width measurements. For Pulse measurements,
refer to the
In a Pulse-Width measurement task, the counter measures the duration of a pulse on a signal.
Figure 3-20 shows an example of a Pulse-Width measurement.
Figure 3-20.
Pulse-Width Measurement
The Pulse-Width can be calculated based on the number of edges of the Counter Timebase
that occur during the pulse on the signal-to-measure. This measurement begins when the
signal-to-measure first enters the active state. If the counter is armed while the signal-to-measure
is already in the active state, then the counter will wait for the next transition to the active state
to begin the measurement.
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