National Instruments PCI-4452 - Manual (Page 41)

Chapter 4 Signal Connections
© National Instruments Corporation 4-11 PCI-4451/4452 User Manual
Analog Output Signal Connections
The analog output signals for the PCI-4451 device are +DAC0OUT,
−
DAC0OUT, +DAC1OUT, -DAC1OUT, and AOGND. +DAC0OUT and
−
DAC0OUT are the plus and minus voltage output signals for analog
output channel 0. +DAC1OUT and
−
DAC1OUT are the plus and minus
voltage output signal, for analog output channel 1.
AOGND is a ground-reference signal for both analog output channels. It is
connected directly to the ground system on the PCI-4451 device. You can
use this signal for a general analog ground tie point to your PCI-4451
device if necessary, but connecting AOGND to other earth-connected
grounds is not recommended. AOGND is not directly available if you are
using the BNC-2140 accessory.
The PCI-4451 has two analog output channels, either of which is illustrated
in Figure 4-4.
Figure 4-4. Analog Output Channel Block Diagram
The analog output stage is differential and balanced. Each output signal
consists of a plus connection, a minus connection, and a ground (AOGND)
connection. The actual output signal is the difference between the plus and
minus connections. The pair is balanced, meaning that, if the impedances
from each of the pair to AOGND is the same (or infinite), then the voltage
at the plus and minus terminals are equal but opposite, so that their
difference is the desired signal and their sum (or average) is zero. If
impedances from each of the pair to AOGND is not the same, the
connection is unbalanced, but the difference between the plus and minus
Balanced
Differential
Driver
Attenuator
D/A
Converter
Gain = 0 dB
Gain = -20 dB
Gain = -40 dB
Gain = -
∞
dB
11
Ω
100 k Ω
10 k
Ω
100 k
Ω
+DAC xOUT
-DAC xOUT
AOGND
11 Ω
User.book Page 11 Tuesday, April 14, 1998 10:20 AM