PINDA Inductive Probe

Testing a PINDA probe. Image from Prusa.

The i3 MK3S uses an inductive probe, called the PINDA, to detect the bed and set the Z coordinates as well as the Z-offset. An inductive probe works by generating an electromagnetic current when it comes into proximity with a metallic object. In this case, the inductive probe senses the spring steel sheet.

Inductive sensors like the PINDA has a certain trigger point, therefore it is important that it is not too far away relative to the nozzle. Otherwise, your nozzle could crash into the bed before the probe triggers!

Offset between the probe and the nozzle relative to the bed surface. Image from 3D Printing Stack Exchange.

The PINDA probe may need to be altered in terms of its mounting as well as its height relative to the nozzle when doing modifications to the toolhead. Examples of these are non planar 3D printing where the nozzle is significantly longer than a regular nozzle. This requires the PINDA probe's mount to be modified so that the probe can be put closer to the nozzle.

You can read more about installing a PINDA probe as well as testing it here:

Prusa KnowledgebasePrusa Knowledgebase

PINDA Probe Testing

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Installing the PINDA probe on the E axis