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I have a picture of a schematic that has these legends on the resistors. What does N/F stand for? And is it also applicable on other electronic components?

Schematic with some resistors marked "N/F"

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    \$\begingroup\$ Not fitted, maybe \$\endgroup\$ – τεκ Jan 17 '18 at 5:52
  • \$\begingroup\$ For completeness: NF with a stated resistance value could also mean that a Non Flammable resistor should go there. \$\endgroup\$ – rackandboneman Jan 17 '18 at 10:21
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    \$\begingroup\$ It's annoying that there are multiple ways to describe this. N/F, NP, adding a star to the name, etc. \$\endgroup\$ – pipe Jan 17 '18 at 14:44
  • \$\begingroup\$ Thanks for all the comments, so would not fitted means that area can be open, i mean put no resistors at all? \$\endgroup\$ – Mheruian Jan 18 '18 at 2:44
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Not fitted. In this case, specifically, the designer wanted to be able to choose whether IN+_2 and IN-_2 should each be connected to either IIN_2A, IIN_2B, or IIN_2C. That's why they used a combination of zero-ohm resistors (which are like wires) and N/F parts.

By selectively mounting zero-ohm resistors to different pads, it allows the designer to reuse the board for different scenarios, or with unknown future configurations.

In the default configuration specified by this schematic, IIN+_2 is directly attached to IIN_2A, and IIN-_2 is directly attached to IIN_2C and IIN_2B.

Because R64 is connected to ground, I assume there was an optional voltage-divider (or digital pull-down) resistor on the design, too.

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  • \$\begingroup\$ Thanks for all the comments, so would not fitted means that area can be open, i mean put no resistors at all? \$\endgroup\$ – Mheruian Jan 18 '18 at 2:44
  • \$\begingroup\$ Correct — do not install anything on those pads. \$\endgroup\$ – Jay Carlson Jan 19 '18 at 20:33
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Not fitted. Used when you want a footprint on a PCB, but don't necessarily want to install a component there.

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  • \$\begingroup\$ I see :D thanks a lot, indeed this was very helpful, there are times i see other PCB boards where there are no components soldered at all on some areas, so those are not fitted components. Would that maybe components that should be placed there are for somewhat calibration or testing? settings? configs? \$\endgroup\$ – Mheruian Jan 18 '18 at 2:47
  • \$\begingroup\$ My guess is economics. It gives the designers options for reconfiguring the circuit without making a new circuit board, and allows using the same circuit board in more than one version of a product. Both save money and time. Parts that are not fitted in production may be fitted for testing and development. \$\endgroup\$ – vofa Jan 18 '18 at 2:55

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