National Instruments NI 4472, Руководство пользователя, Страница: 30 / 73

Chapter 3 Device Overview and Theory of Operation
© National Instruments Corporation 3-3 NI 4472 User Manual
is protected to ±42.4 V, whether power is on or off. The shield side of the
analog input channels has no overvoltage protection. Do
not apply a signal
that varies by more than ±2.5 V from the ground of the NI 4472.
Analog Input Signal Connections
Figure 3-3 shows a diagram of one of the eight identical NI 4472 analog
input stages.
Figure 3-3. Analog Input Stage
The analog input stage presents high input impedance to the analog input
signals connected to your NI 4472. Signals are routed to the positive inputs
of the analog input stage, and their returns are routed to AIGND through a
common-mode choke. Your NI 4472 ADCs measure these signals when
they perform A/D conversions.
These input channels have 24-bit resolution and are simultaneously
sampled at software-programmable rates from 102.4 kS/s down to 1.0 kS/s
in 190.7 µS/s increments for
f
s
> 51.2 kS/s or 95.37 µS/s increments for
+
–
Differential
Buffer
Common-Mode
Choke
Calibration
Multiplexer
1 M
Ω
0.047
µ
F
DC/AC
Coupling
Analog-
Lowpass
Filter
A/D
Converter
CH0
Gain = –12.77 dB
0.01
µ
F
50
Ω
0.01
µ
F
ICP
On/Off
24 V Compliant
ICP Current
Source
4 mA