Chapter 3
Hardware Overview
©
National Instruments Corporation
3-7
PCI-4451/4452/4453/4454 User Manual
♦
PCI-4453
The PCI-4453 operates in SE mode using the BNC-2142 DSA accessory.
For more information, refer to the BNC-2142 Installation Guide.
Output Polarity and Output Range
The PCI-4451/4453 operates in bipolar mode. Bipolar output means that
the output voltage range is between –V
ref
/2 and +V
ref
/2. The PCI-4451 has
a bipolar output range of 20 V (±10 V) for an attenuation of 1.0 (0 dB).
All data written to the DACs are interpreted as two’s complement format.
In two’s complement mode, data values written to the analog output
channel are either positive or negative.
Note
When the DACs no longer have data written to them, they automatically retransmit
the last data point they received. If you are expecting the data to return to 0 V or any other
voltage level, you must append the data to make it do so.
♦
PCI-4451
You can configure the range settings on each output channel independently.
The software-programmable attenuation on these devices increases their
overall flexibility by matching the output signal ranges to the your
application. Table 3-2 shows the overall output range and resolution
according to the attenuation used.
Table 3-2.
Actual Output Range and Resolution of the PCI-4451
Attenuation
Linear
Attenuation
dB
Range
Resolution
1
1.0
0 dB
±10.0 V
305.18 µV
10
20 dB
±1.00 V
30.158 µV
100
40 dB
±0.100 V
3.0518 µV
∞
∞
dB
0 V
0 V
1
The value of 1 LSB of the 16-bit DAC; that is, the voltage increment corresponding to a
change of one count in the DAC 16-bit count.
See Appendix A,
, for absolute maximum ratings.
