Working Principle : Non-buried NPN normally open capacitive proximity switch It could work with any kinds of bed materials, such as glasses, woods, metals, and so on It is an auto leveling sensor for 3D Printers based on open-source. Product Description: Model: M12 capacitive proximity switch Installation type: non-embedded Action mode: NPN normally open Size: M12 x 62mm Wiring length 510mm Shell nickel plated brass, detection surface ABS Detection distance: 5mm +/- 10% Lag distance: less than 10% of the detection distance Detection object: metal, non-metal: plastic, glass, wood, liquid: water, oil, etc. Voltage: DC 6-36V Operating environment temperature: -25°C-65°C, no freezing Use environment humidity: 35-95%RH Colour: Silver Material: Metal Package Contents: 1 x Proximity Sensor Attention: Please remarks the 3d printer model in your order. Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.