©
National Instruments Corporation
B-1
Analog Output Series User Manual
B
Troubleshooting
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
. It contains thousands of documents that
answer frequently asked questions about NI products.
Calculating Frequency Resolution
How can I calculate the frequency resolution of the analog output on
the AO Series device?
The analog frequency (
f
a
) you can generate is determined by the update
clock frequency (
f
u
) and the number of samples per cycle (
S
c
):
The onboard 20 MHz clock that generates
f
u
can only be divided by an
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
u
equals 100 kHz. The 20 MHz clock must be divided by 200 as
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
u
equals 99.5 kHz, as the
following equation shows:
f
a
f
u
S
c
-----
=
2 kHz
f
u
50
------
=
20 MHz
200
-------------------
100 kHz
=
20 MHz
201
-------------------
99.50 kHz
=