ADLINK DAQe-2214 - Manual (Page 59)

Operation Theory 47
4.2 D/A Conversion
NOTE The DAQ-/DAQe-2213 card does not support this func-
tion.
There are two 12-bit D/A output channels available in the DAQ-/
DAQe-/PXI-2204/2205/2206 card. When using D/A converters,
you should assign and control the D/A converter reference
sources for the D/A operation mode and D/A channels. You could
also set the output polarity to unipolar or bipolar.
The reference selection control lets you utilize in full the multiply-
ing characteristics of the D/A converters. Internal 10V reference
and external reference inputs are available in the DAQ-/DAQe-
2214 card. The range of the D/A output is directly related to the
reference. The digital codes that are updated to the D/A convert-
ers will multiply with the reference to generate the analog output.
While using internal 10V reference, the full range would be –10V
to +9.9951V in the bipolar output mode, and 0V to 9.9976V in the
unipolar output mode. While using an external reference, you can
reach different output ranges by connecting different references.
For example, if connecting a DC –5V with the external reference,
then you can get a full range from –4.9976V to +5V in the bipolar
output with inverting characteristics due to the negative reference
voltage. You could also have an amplitude modulated (AM) output
by feeding a sinusoidal signal into the reference input. The range
of the external reference should be within ±10V. Table 4-3 and
Table 4-4 illustrates the relationship between digital code and out-
put voltages with Vref=10V and if internal reference is selected.
Digital Code Analog Output
111111111111 Vref * (2047/2048)
100000000001
Vref * (1/2048)
100000000000 0V
011111111111 -Vref * (1/2048)
000000000000 -Vref
Table 4-3: Bipolar Output Code Table