National Instruments SCXI-1121 User Manual
Page 49
Chapter 2
Configuration and Installation
© National Instruments Corporation
2-33
Terminal Block Signal Connection
Warnings
The chassis GND terminals on your terminal block are for grounding high
impedance sources such as a floating source (1 mA maximum). Do not use these terminals
as safety earth grounds.
If high voltages (
≥
42 V
rms
) are present, you must connect the safety earth ground to the
strain-relief tab. This complies with UL 1244 and fully protects against electric shock when
the terminal block is not connected to the chassis. To connect the safety earth ground to the
strain-relief tab, run an earth ground wire in the cable from the signal source to the terminal
block. National Instruments is not liable for any damages or injuries resulting from
inadequate safety earth ground connections.
Shock Hazard—This unit should only be opened by qualified personnel aware of the
dangers involved. Disconnect all power before removing cover. Always install grounding
screw.
To connect the signal to the terminal block, use the following procedure:
1.
Remove the grounding screw of the top cover.
2.
Snap out the top cover of the shield by placing a screwdriver in the
groove at the bottom of the terminal block.
3.
Slide the signal wires, one at a time, through the front panel
strain-relief opening. You can add padding or insulation if necessary.
4.
Connect the wires to the screw terminals. For thermistor and RTD
connection, follow the procedure stated in the
section earlier in this chapter.
5.
Tighten the larger strain-relief screws.
6.
Snap the top cover back in place.
7.
Reinsert the grounding screw to ensure proper shielding.
8.
Connect the terminal block to the SCXI-1121 front connector as
explained in the
chapter.
Figure 2-11 shows a parts locator diagram for the SCXI-1320 terminal
block. Figure 2-12 shows a parts locator diagram for the SCXI-1328
terminal block. Figure 2-13 shows a parts locator diagram for the
SCXI-1321 terminal block.