National Instruments RMX-410 Series, User Manual, Page: 38 / 132

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NATIONAL
INSTRUMENTS
3.9.3 Wire Termination
The wires should be properly terminated with terminals securely attached. DO NOT use non
terminated wires for load connection at the power supply.
CAUTION:
When local sensing, a short from +LS or +S to -V or -S or -LS, will cause damage to the power supply.
Reversing the sense wires might cause damage to the power supply in local and remote sensing.
(Do not connect -S to +V or +S to -V.)
3.9.4 Noise and Impedance Effects
To minimize the noise pickup or radiation, the load wires and remote sense wires should be twisted
pairs to the shortest possible length. Shielding of sense leads may be necessary in high noise
environments. Where shielding is used, connect the shield to the chassis via a rear panel Ground
screw. Even if noise is not a concern, the load and remote sense wires should be twisted-pairs to
reduce coupling, which might impact the stability of power supply. The sense leads should be
separated from the power leads.
Twisting the load wires reduces the parasitic inductance of the cable which could produce high
frequency voltage spikes at the load and the output of power supply, because of current variation
in the load itself.
The impedance introduced between the power supply output and the load could make the ripple
and noise at the load worse than the noise at the power supply rear panel output. Additional
filtering with bypass capacitors at the load terminals may be required to bypass the high frequency
load current.
3.9.5 Inductive Loads
Inductive loads can produce voltage spikes that may be harmful to the power supply. A diode
should be connected across the output. The diode voltage and current rating should be greater
than the power supply maximum output voltage and current rating. Connect the cathode to the
positive output and the anode to the negative output of the power supply.
Where positive load transients such as back EMF from a motor may occur, connect a surge suppressor
across the output to protect the power supply. The breakdown voltage rating of the suppressor
must be approximately 10% higher than the maximum output voltage of the power supply.
3.9.6 Making the Load Connections
WARNING:
There is a potential shock hazard when using a power supply with an output voltage greater than
60VDC. To protect personnel against accidental contact with hazardous voltages, ensure that
the protection of output bus-bars and output connectors is mounted and properly assembled.
Ensure that the load and its connections have no accessible live parts. Ensure that the load wiring
insulation rating is greater than or equal to the maximum output voltage of the power supply.