Hi guys,
So I'd like to purchase this sensor: https://www.festo.com/cat/en-il_il/products_SPAN?CurrentPartNo=8035553 in order to measure vacuum.

It's just unclear to me, in the electrical connections; what difference does it make if I pick "PN PNP or NPN" or the second option which is "PNLK PNP or NPN or IO-Link" ? I'm not gonna use a switch option but I'd like to know what it means if I pick one and not the other.

Furthermore, how can it even act as a switch if only has 1 pneumatic connection?

 

Did you try Google?

http://www.schneider-electric.co.uk/en/faqs/FA142566/

 

I did try google, and your link doesn't really answer much; it mentions nothing about IO-Link or PNLK; in addition the title is about 3 wires not 4 wires.

More importantly, don't they sell vacuum sensors without that PNP/NPN connection? What if I don't wanna use a PLC? What if I just want it to measure vacuum?

 

It is stated in the Data Sheet.

https://www.festo.com/cat/en-il_il/data/doc_engb/PDF/EN/SPAN_EN.PDF

Pin-3 is the analog output.

 

It's just unclear to me, in the electrical connections; what difference does it make if I pick "PN PNP or NPN" or the second option which is "PNLK PNP or NPN or IO-Link" ? I'm not gonna use a switch option but I'd like to know what it means if I pick one and not the other.

It depends on the device you are interfacing the sensor with, here is an article on sinking and sourcing.
That sensor uses IO-Link for connection to the receiving device.
Max.