According to its operating principles, the sensor detects the capacitance between the sensor electrode and ground. When a high-frequency voltage of several hundreds of kHz or higher (common mode noise) to ground is superimposed on the sensor power line, it will interfere with sensor operation, and the following malfunctions could result; higher detection sensitivity, detection stuck ON at all times, or deterioration of internal parts/components.

Typical sources of common mode noise are as follows (including wiring of each):
・Inverter devices (power supplies for inverter motors and pulse motors)
・Vibration generators
・Switching power supplies
・Wireless devices
・Microwave generators
・Large power transmission antennas
To prevent the generation of common mode noise, it is essential to ground near these noise sources.

To avoid common mode noise generation in the sensor power line, connect the sensor ground (GND, 0V) either directly to ground, or to ground via a 1,000 pF or higher capacitor of sufficient withstand voltage, or else to the frame ground (F.G.) with sufficient capacitance to ground. When connecting the sensor to ground via the sensor housing, ensure correct electrical bonding to avoid contact resistance.There is also another type of noise referred to as normal mode noise (or differential mode noise) which is generated in-between the power lines. If the current, cable loop area, and frequency are the same, common mode noise is much larger by around 100 times (100 MHz) to 10,000 times (1 MHz) compared to normal mode noise. Accordingly, a countermeasure of simply separating the line experiencing the common mode noise from the sensor wiring is insufficient and not recommended.To avoid common mode noise, use a shielded cable, or more effectively, adequate shield grounding should be used.

Influence of Surrounding Metal