National Instruments AT-MIO-16X - Manual (Page 61)

Chapter 2 Configuration and Installation
© National Instruments Corporation 2-39 AT-MIO-16X User Manual
To measure frequency, a counter is programmed to be level gated and
the rising or falling edges are counted in a signal applied to a SOURCE
input. The gate signal applied to the counter GATE input is of some
known duration. In this case, the counter is programmed to count either
rising or falling edges at the SOURCE input while the gate is applied.
The frequency of the input signal is then the count value divided by the
known gate period. Figure 2-18 shows the connections for a frequency
measurement application. A second counter can also be used to generate
the gate signal in this application.
Figure 2-18. Frequency Measurement Application
Two or more counters can be concatenated by tying the OUT signal
from one counter to the SOURCE signal of another counter. The
counters can then be treated as one 32-bit or 48-bit counter for most
counting applications.
Signal
Source
DIG GND
Counter
OUT
SOURCE
GATE
+5 V
4.7 k
Ω
I/O Connector
AT-MIO-16X Board
Gate
Source