National Instruments SCC-CI20 User Manual page 4

Replacing the Input Resistors
SCC-CI20 Current Input Module User Guide
channel X. The value of X is determined by the number of the SC-2345
socket, J(X+1) or J(X+9), where you plug in the SCC-CI20. Figure 1 shows
the SCC-CI20 signal connections.
SCC-C120
Signal
Source
4
3
2
1
Signal source may be floating or ground-referenced.
Figure 1. SCC-CI20 Signal Connections
The input signal source can be floating or ground-referenced. The
SCC-CI20 has high-impedance bias resistors typically required for floating
sources, so you do not need external bias resistors referenced to ground.
Incorrect connections can damage the input resistors and possibly other
components of the module. Spare 249 Ω resistors are available inside the
SCC-CI20. To open the SCC-CI20, complete the following steps:
1. Remove the screw from the back (wide unlabeled side).
2. Turn the front (wide labeled side) toward you.
3. Place the screw-terminal receptacle to the left.
4. Slide the top cover to the right.
5. Lift off the cover.
Overvoltage
Protection
+
R3
–
Overvoltage
Protection
10 MΩ
Overvoltage
Protection
+
R2
–
Overvoltage
Protection
10 MΩ
4
E Series DAQ Device
AI (X )
AI SENSE
AI GND
AI (X+8)
ni.com