What is the difference between 2-wire proximity sensors and 3-wire proximity sensors?
Proximity sensors usually have an integrated LED. In the case of a 2-wire proximity sensor, therefore, the LED is connected in series, causing a voltage drop of 3…4 volts. In contrast, in the case of a 3-wire proximity sensor, the LED is integrated in parallel with the result that it does not cause a voltage drop. 2-wire reed switches without an LED are also not subject to a voltage drop.
