Chapter 2
Using the NI 447X
©
National Instruments Corporation
2-7
•
Whether AC or DC coupling is best for your application
Note
Use AC coupling when IEPE signal conditioning is enabled to remove any DC
offset caused by the IEPE transducer. Using DC coupling with IEPE is appropriate only
if the impedance of the sensor does not exceed 2.5 k
Ω
and you are acquiring very low
frequency signals.
•
The voltage range of the input signal
Signal Sources
The AI channels of the NI 447
X
have unbalanced differential inputs.
Figure 2-3 shows the input configurations for floating and grounded signal
sources.
Figure 2-3.
Input Configurations for the NI 447
X
Caution
Connecting a signal that varies more than ±2.5 V from the ground reference of
the NI 447
X
to the ground (shield) of any AI channel can result in inaccurate measurements
or damage to the device. NI is
not
responsible for damage caused by such connections.
Floating
Source
NI 447
X
Grounded
Source
Signal
Ground
Signal
Ground
+
–
+
–
+
–
+
–
CH
n
CH
n
NI 447
X
50
Ω
50
Ω
1 M
Ω
1 M
Ω
