RS or Remote Sense wires on select power supplies are a feature used to correct for the small voltage loss across the load wires or any other connections from the power supply output terminals to the load terminals. This feature is typically used in low-voltage high-current systems, circuits requiring precise voltage, or when long stretches of output wire are present. As load currents fluctuate the voltage drop across the load wires and connections will also change.By connecting the RS wires properly, the power supply will adjust the output voltage accordingly to help keep the voltage steady at the load.
Every supply will vary, but it is common to see a supply to compensate the voltage output by about 0.5v max give or take such like that on the HRPG-300-12 model from Mean Well. The voltage change on well designed supplies is usually less than the voltage change to the output when adjusting the V ADJ (voltage adjust) potentiometer.
Wiring
Depending on your design, smaller wire gauge such as 22AWG is typically alright to use for the remote sense wires as these lead to a high impedance circuit so it will not draw a lot of current. The RS wires are simply run to the actual load terminals and bypass the actual load wires. Polarity must be uniform, meaning positive RS wire to positive load terminal, and negative RS wire to negative load terminal, or damage to supply can result. Sometimes a shielded cable is desirable especially in noisy environments or long RS cable runs.
A given supply will either require that the sense terminals be connected (either locally or remotely) for proper function, or not. If not, which is usually the case then this input can be left open, as a user-supplied local bypass typically won’t make much difference. This will all depend on internal RS circuit configuration of the power supply. Generally speaking, the power supplies that do not come provided with the RS cable are not required to be used.
RS Bypass
A quick way to resolve remote sense floating issues and bypass this feature is to jumper the positive remote sense wire to the positive supply output and jumper the negative remote sense wire to the negative supply output otherwise known as local sensing or bypass. Do not mix polarities as this may damage the power supply.
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See Also:
How to use remote sensing in series/parallel connection?
Example Datasheet
https://www.meanwell.com/Upload/PDF/HRPG-300/HRPG-300-SPEC.PDF