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Chapter 3
Analog Output
AO Range
±10 V
±EXT REF
Analog Output Resolution
You can calculate the least significant bit (LSB), or the minimal allowed voltage change, on a
voltage output on your AO Series device as follows:
where the output range is determined by your reference selection. Using AO EXT REF, you can
reduce the output voltage range and lower the LSB, the minimum allowed voltage change. For
more information on using the AO External Reference signal, refer to the
(NI 6711/6713/DAQCard-6715 and NI 6731/6733 Only)
The following equation is an example of this formula using the NI 6731/6733.
The denominator in the equation is derived from 2
use 16-bit DACs.
Reference Selection (NI 6711/6713/DAQCard-6715 and
NI 6731/6733 Only)
You can connect each DAC to the device internal reference of 10 V or to the external reference
signal connected to the external reference (AO EXT REF) pin on the I/O connector. This signal
applied to AO EXT REF should be within ±11 V of AO GND. You do not need to configure all
channels for the same mode. Using AO EXT REF to reduce the output voltage range results in
a higher resolution at the adjusted range.
Reglitch Selection (NI 6711/6713 Only)
In normal operation, a DAC output glitches whenever it is updated with a new value. The glitch
energy differs from code to code and appears as distortion in the frequency spectrum. Each AO
channel contains a reglitch circuit that generates uniform glitch energy at every code rather than
large glitches at the major code transitions. This uniform glitch energy appears as a multiple of
the update rate in the frequency spectrum. This reglitch circuit does not eliminate the glitches; it
only makes them more uniform in size. By default, reglitching is disabled for all channels;
however, you can use NI-DAQ to independently enable reglitching for each channel.
3-2 | ni.com
Table 3-1. AO Reference Selection Options
Polarity
Bipolar
Bipolar
LSB = output voltage range/2
20 V
--------------- -
65,536
Reference Select
Internal
AO External Reference Signal
resolution of your device
section.
305 μV
=
16
= 65,536, since the NI 6731/6733 devices
Reference Selection
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