Troubleshooting - National Instruments NI 6711 User Manual

Troubleshooting

Calculating Frequency Resolution
© National Instruments Corporation
This section contains some common questions about AO Series devices. If
your questions are not answered here, refer to the National Instruments
KnowledgeBase at
ni.com/kb
answer frequently asked questions about NI products.
How can I calculate the frequency resolution of the analog output on
the AO Series device?
The analog frequency (f
clock frequency (f ) and the number of samples per cycle (S
u
The onboard 20 MHz clock that generates f
integer. For example, suppose you want to generate a sine wave at 2 kHz
with 50 samples per cycle. Substitute 2 kHz and 50 samples into the
previous equation to get:
So f equals 100 kHz. The 20 MHz clock must be divided by 200 as
u
shown by:
Suppose now you want to slightly increase or decrease the frequency of the
sine wave. The closest available update clock you can generate occurs using
a divisor of 199 or 201. If you choose 201, f
following equation shows:
. It contains thousands of documents that
) you can generate is determined by the update
a
f
u
f
= ---- -
a
S
c
u
f
u
2 kHz
= ----- -
50
20 MHz
100 kHz
------------------- =
200
u
20 MHz
99.50 kHz
------------------- =
201
B-1
B
):
c
can only be divided by an
equals 99.5 kHz, as the
Analog Output Series User Manual