National Instruments NI 9233 - Manual (Page 9)

© National Instruments Corp. 9 NI 9233 Operating Instructions and Specifications
The NI 9233 analog input channels are referenced to the chassis
ground through a 50
Ω resistor. To minimize ground noise, make
sure that the chassis ground is connected to the earth ground. Each
channel is protected from overvoltages. The NI 9233 provides
an IEPE excitation current for each input signal. The signal is
AC-coupled, buffered, and conditioned. The signal is then sampled
by a 24-bit Delta-Sigma ADC. The NI 9233 IEPE excitation
current and AC coupling are always enabled. Refer to Figure 4 for
an illustration of the input circuitry for one channel of the NI 9233.
Figure 4. Input Circuitry for One Channel of the NI 9233
NI 9233
AI+
AI–
50
Ω
ADC
Amplifier
and
Prefilter
Excitation
Current
AC
Coupling
+