Ao Reference Selection - National Instruments DAQ X Series User Manual

Chapter 5 Analog Output
•
•

AO Reference Selection

AO reference selection allows you to set the analog output range. The
analog output range describes the set of voltages the device can generate.
The digital codes of the DAC are spread evenly across the analog output
range. So, if the range is smaller, the analog output has better resolution;
that is, the voltage output difference between two consecutive codes is
smaller. Therefore, the analog output is more accurate.
The analog output range of a device is all of the voltages between:
The possible settings for AO reference depend on the device model. For
models not described below, refer to the specifications for your device.
•
•
When using an external reference, the output signal is not calibrated in software. You
Note
can generate a value and measure the voltage offset to calibrate your output in software.
X Series User Manual
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
AO Sample Clock—The AO Sample Clock signal reads a sample
from the DAC FIFO and generates the AO voltage.
AO Reference Selection—The AO reference selection signal allows
you to change the range of the analog outputs.
–AO Reference and +AO Reference
On NI 6321/6323/634x devices, the AO
(NI 6321/6323/634x Devices)
reference is always 10 V. So, for NI 6321/6323/634x devices, the
analog output range equals ±10 V.
On NI 635x/636x devices, the AO reference of
(NI 635x/636x Devices)
each analog output (AO <0..3>) can be individually set to one of the
following:
– 10 V
– 5 V
– APFI <0,1>
You can connect an external signal to APFI <0,1> to provide the AO
reference. The AO reference can be a positive or negative voltage. If
AO reference is a negative voltage, the polarity of the AO output is
inverted. The valid ranges of APFI <0,1> are listed in the device
specifications.
You can use one of the AO <0..3> signals to be the AO reference for a
different AO signal. However, you must externally connect this
channel to APFI 0 or APFI 1.
5-2 ni.com