The sense lines enable the measurement of the actual encoder voltage (without the distortion caused by voltage drops due to the supply current and cable resistance).
Due to the voltage drop in the cables for the supply voltage, the encoder input voltage Vin is less than the voltage output Vout from the power supply.
The input voltage Vin supplied to the encoder will then be output to the sense power supply voltage (VCC) and the sense ground (GND) lines and fed back to the power supply unit as data.
The input resistance Ri on the power supply unit should be at least 22 MOhm so that there will be no voltage drop on these lines.
With power supply units with sense input, the output voltage Vout can now be readjusted automatically.