Chapter 3 Signal Connections
SCXI-1120/D User Manual 3-2 www.natinst.com
When using the device with high common-mode voltages, you
MUST
insulate your signal
wires for the highest input voltage. National Instruments is not liable for any damages or
injuries resulting from inadequate signal wire insulation. Use only 26 to 14 AWG wire with
a voltage rating of 300 V and 60 °C for measuring 250 to 300 V; use only 600 V and 60 °C
for measuring 480 V. Prepare your signal wire by stripping the insulation no more than
7mm.
When connecting or disconnecting signal lines to the SCXI terminal block screw terminals,
make sure the lines are powered off. Potential differences between the lines and the SCXI
ground create a shock hazard while you connect the lines.
When using this module with a terminal block, connect the signal wires to the screw
terminals by inserting the stripped end of the wire fully into the terminals. Tighten the
terminals to a torque of 5 to 7 in.-lb.
Connections, including power signals to ground and vice versa, that exceed any of the
maximum signal ratings on the SCXI device, can create a shock or fire hazard or can
damage any or all of the devices connected to the SCXI chassis, the host computer, and the
SCXI device. National Instruments is not liable for any damages or injuries resulting from
incorrect signal connections.
If high voltages (≥30 V
rms
and 42.4 V
peak
or 60 VDC) are present, you must connect a
safety earth ground wire to the terminal block safety ground solder lug. This complies with
safety agency requirements and protects against electric shock when the terminal block is
not connected to the chassis. To connect the safety earth ground to the safety ground solder
lug, 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.
Do not loosen or re-orient the safety ground solder lug hardware on the terminal block
when connecting the safety ground wire. To do so reduces the safety isolation between the
high voltage and safety ground.
Clean devices and terminal blocks by brushing off light dust with a soft, nonmetallic brush.
Remove other contaminants with deionized water and a stiff nonmetallic brush. The unit
must be completely dry and free from contaminants before returning to service.
Use only National Instruments high voltage TBX Series cable assemblies with
high-voltage TBX Series terminal blocks.
Caution To comply with the UL North America or CE, use this module with a UL or CE
marked SCXI chassis.
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