Is the GND in the control pin of the servo driver usually a ground wire or a negative pole of the power supply?

When using a servo (Panasonic) to return to the origin in a recent project, if other axes are also moving, the Z-phase zero point signal received by the PLC is easily lost, resulting in abnormal return to the origin position. Later, upon checking the driver manual, it was discovered that the GND of the Z-phase zero point signal needed to be connected to the common terminal of the switch power supply. After rewiring, it returned to normal.
Upon consulting information, it was found that GND does not mean ground wire, but rather a reference point for zero potential.
How do you distinguish between GND grounding wire and power negative pole?