My target is a 20mm long, stainless steel, socket head, M3 screw with head facing the sensor. How will sensor sensitivity, i.e. maximum sensing distance, change with different sensor size? I'm looking at Pepperl+Fuchs datasheets, but they use targets with the sizes proportional to the sensor size, so fixed size target comparison is not possible. M12 cylindrical sensor is specified with a 12mm x 12mm x 1mm target, M8 with a 8mm x 8mm x 1mm target.

Should my sensor size, i.e. diameter of cylindrical type, approximately match my target size? The head of my M3 screw has 5.4mm diameter. Will a larger diameter sensor, e.g. M8 or M12, have lower than specified maximum sensing distance with my target?

  • \$\begingroup\$ Stainless steel may not be detected at all depending on the sensor tech. \$\endgroup\$
    – Andy aka
    Commented Mar 28, 2023 at 9:54
  • \$\begingroup\$ @Andyaka Several brands of inductive proximity sensors work just fine with 304 stainless steel. The sensing distance is reduced, e.g. 0.78 factor for Pepprl+Fuchs. \$\endgroup\$ Commented Mar 28, 2023 at 17:22
  • \$\begingroup\$ Try 316 stainless steel for instance but, it depends on the tech @paul. \$\endgroup\$
    – Andy aka
    Commented Mar 28, 2023 at 17:30

1 Answer 1


The maximum operating distance of an inductive proximity switch is the distance to the point at which the sensor first detects the 'standard target' as it slowly approaches the sensing head.

For example, the 'standard target' for a M10 inductive proximity switch is a mild steel sheet of size 10mm x 10mm x 1mm.

The maximum operating distance gets reduced with a 'smaller-than-specified' target size.

  • \$\begingroup\$ Do you have a datasheet showing this reduction? \$\endgroup\$ Commented Mar 28, 2023 at 17:37
  • \$\begingroup\$ It's not been provided in the datasheets. \$\endgroup\$
    – vu2nan
    Commented Mar 29, 2023 at 2:06

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