Working Principle : Non-buried NPN normally open capacitive switch It could work with any kinds of bed materials, such as glasses, , metals, and so on It is an auto leveling sensor for 3D Printers based on open-source. Product Description: Model: M12 capacitive switch Installation type: non-embedded Action mode: NPN normally open Size: M12 x 62mm Wiring length 510mm Shell plated brass, detection surface ABS Detection distance: 5mm +/- 10% distance: less than 10% of the detection distance Detection object: metal, non-metal: plastic, glass, wood, liquid: water, oil, etc. : 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 Sensor Attention: remarks the 3d printer model in your order. Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.