© National Instruments | 1-19
RMX Programmable Power Supplies User Manual
Local Sensing
By factory default, RMX programmable power supplies are set to local sensing (the rear panel
sensing connector is hard wired). The sensing point during local sensing is the output terminal.
This method does not compensate for the voltage drop across the load cable, so use this method
when the load current is small or when you do not need to consider the load effect voltage.
Figure 1-20. Local Sensing
Remote Sensing
Remote sensing is a feature that reduces the effect of voltage drops across load cabling
resulting in a more accurate voltage being applied at the terminals of the load.
Refer to Appendix A, Specifications for the maximum voltage drop each RMX power supply's
remote sense terminals can compensate for. Select a load cable that has sufficient current
capacity to prevent the voltage drop in the load cable from exceeding the compensation voltage.
Refer to the Load Cables section for more information about the cables.
When using remote sensing, the output terminals compensate for the voltage drop across the load
cabling by increasing the output voltage above the programmed setpoint until the sense leads
detect the programmed setpoint at the load itself. This requires the output terminals to generate
a voltage that is greater than the programmed voltage level. If you are performing remote sensing
with the voltage close to the maximum output voltage of the power supply, the total output is
still limited by the maximum output voltage at the terminals of the power supply (105% of the
rated output voltage). If the signal doesn’t seem to be stable, an electrolytic capacitor may be
required at the sensing point (across the load).
To minimize noise on the output signal, use twisted-pair wires or 2-core shielded wires. Connect
the ground of your shielded wire to the ground of the RMX programmable power supply or the
load.
+
–
+LS
+S
-LS
-S
Output terminal
Chassis terminal
Sensing terminal
RMX
Load
Use twisted-pair wires for the load cables.
Make the cables as short as possible.
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