ADLINK PXI-2208 - Manual (Page 66)

54 Operation Theory
4.2 D/A Conversion
NOTE The DAQ-/DAQe-/PXI-2208 card does not support this
function.
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-/
PXI-2204/2205/2206 card. The range of the D/A output is directly
related to the reference. The digital codes that are updated to the
D/A converters will multiply with the reference to generate the ana-
log 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 ref-
erence, you can reach different output ranges by connecting differ-
ent 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 ref-
erence input. The range of the external reference should be within
±10V. Table 4-5 and Table 4-6 illustrates the relationship between
digital code and output voltages with Vref=10V and if internal ref-
erence is selected.
Digital Code Analog Output
111111111111 Vref * (2047/2048)
100000000001 Vref * (1/2048)
100000000000 0V
011111111111 -Vref * (1/2048)
000000000000 -Vref
Table 4-5: Bipolar Output Code Table