What is the difference of NPN transistor output and PNP transistor output of the sensor?
(1) NPN output type is used when connecting a load between power supply + and sensor output terminal.
(2) PNP output type is used when connecting a load between sensor output terminal and power supply -.
This type is used a lot in Europe from the viewpoint on safety because the load is not driven even if somewhere of the wiring connected with the sensor output terminal is short-circuited with power supplies in some factors.
(3) The following is output circuit diagram of the E2E as typical.