Wiring Power to the Chassis
The NI 9157/9159 requires an external power supply that meets the specifications. The
NI 9157/9159 filters and regulates the supplied power and provides power for all of the I/O
modules. You must connect a power supply to at least one pair of V and C terminals.
Optionally, you can connect a second power supply to the other pair of V and C terminals. The
chassis draws power from the power supply with the higher voltage. The NI 9157/9159 has
one layer of reverse-voltage protection. Complete the following steps to connect a power
supply to the chassis.
1.
Connect the positive lead of the power supply to the V1 or V2 terminal of the
COMBICON connector shipped with the NI 9157/9159.
2.
Connect the negative lead of the power supply to one of the C terminals of the
COMBICON connector.
3.
Optionally you can connect the positive lead of another power supply to the other V
terminal and the negative lead to one of the C terminals.
4.
Install the COMBICON connector on the front panel of the NI 9157/9159.
Note
The chassis draws power from either V1 or V2 depending on which
terminal has a higher voltage. It does not draw power from both terminals. The
chassis switches between V1 and V2 without affecting operation.
Note
If you prefer for the chassis to draw power from one power supply, you
must ensure that the voltage of that power supply, measured at the chassis
power connector, is at least 500 mV higher than the voltage of the other power
supply.
Caution
The C terminals are internally connected to each other. If you use
two power supplies, make sure that they share a common ground.
Caution
The C terminals are internally connected to the body of the chassis to
prevent a faulty ground connection from causing the chassis ground to float. If
you reverse the input voltage, the positive input voltage is connected directly to
the chassis. The chassis has built-in reversed-voltage protection, but reversed
voltage can damage connected peripherals if the chassis ground is not reliably
connected to earth ground.
Caution
Do not tighten or loosen the terminal screws on the power connector
while the power connector is plugged into the chassis or while the power
supply is on.
Connecting One or More NI 9157/9159 Chassis
to the MXI-Express Host System or a Target
Complete the following steps to connect one or more NI 9157/9159 chassis to a MXI-Express
host system or a target.
NI 9157/9159 User Manual and Specifications
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© National Instruments
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