NI C Series Getting Started

both the high and low times prior to the first measurement becoming ready. Refer to
your soware documentation for more information on arming the counter.
Frequency/Period Measurement
You can take frequency or period measurements with the NI-9361.
The counter measures and returns the period information of a signal. The NI-9361
supports a few frequency measurement methods depending on the settings set by
the user. The NI-9361 returns the current period measurement values when the
counter is read. The measurement values consist of the number of full periods of the
signal-to-measure measured and also the duration of these full periods in the
number of ticks of the 100 MHz counter timebase.
You can calculate the signal period using the following equation:
Signal Period =
N
ticks
× T
base
N
periods
where
■
T
base
is the counter timebase period which is 10 ns
■
N
ticks
is the number of ticks of the counter timebase that elapsed during the
measurement
■
N
periods
is the number of full periods of the signal-to-measure measured
You can calculate the frequency using the following equation:
Signal Frequency
=
1
Signal Period
Channel Settings
You can configure the following counter properties:
■
Input terminal of the signal-to-measure.
■
The active edge, rising or falling, the NI-9361 begins the measurement.
■
Maximum measurable period—You can set the maximum measurable period
of the signal. If the input signal period is slower than this value, the counter
returns a measurement value of zero. Use this property to get updated
measurement data when the signal slows down or is stopped instead of
previous measurements. To disable this feature, set the maximum measurable
period to zero. When this feature is disabled, the counter keeps measuring
© National Instruments
17
NI-9361 Getting Started

NI C Series Specifications

General

Brand	NI
Model	C Series
Category	Control Unit
Language	English